Not all racks play well with all panniers. Ortliebs have a lot of adjustability, generally they fit well on most good quality racks.
Not familiar with Tortec. I am most familiar with Tubus, my favorite touring rear rack is Tubus Logo EVO. That rack is great for panniers, but less useful if you are only carrying something on the top of the rack because it is quite narrow. I use the logo for touring, but use a wider rack for general riding near home.
Some but not all bar bags can be easily removed for you to take with you into a store or restaurant. I have not used an Ortlieb but Ortlieb handlebar bags do have a strong following. The handlebar bags that I use have been out of production for several years, plus I made some major modifications to them so I do not recommend them.
Not sure why you are opposed to drop bars, being a roadie I assumed you would see the advantage of using drops in headwinds. I can't offer any advice on alternative bars. I am 67 years old, over a decade ago I did not use drop bars as much as I do now, but that was before I lost 15 percent of my body weight, which also reduced my pants waist size. With that weight loss, the drops are more comfortable to use. My drop bars, top of bar is roughly the same height as the top of my saddle or maybe up to 10mm lower. Thus, my drops are much higher than on a typical road bike. I use the Hubbub adapter on my Nomad Mk II to mount the Rohloff shifter to the right side handlebar end.
Saddles, if you have been happy with non-leather saddles, stick with non-leather. Some people like the Brooks Cambium saddles, they are non-leather and do not require the maintenance of leather. I tried two Cambium saddles and was not happy, but I have generally not been happy with non-leather saddles. But I know some long distance riders that like the Cambium saddles. Only you will know if they work for you.
If your bum on a five day road riding holiday was happy, on a long tour it would likely also be happy. If you used the drops on a road bike but do not have drops on a tour bike, you would be sitting more upright on a tour bike than on a road bike. Thus, you might want a wider saddle that is flatter in back on a tour bike. I on the other hand have drop bars on almost all my bikes, including touring bikes. And I use the drops, thus I want the same saddle shape on a tour bike as a road bike.
Somedays on a tour you have longer days. I have had 12 to 14 hour days on a tour bike, not often, but often enough. If you have done some long randonneuring or audax events, then you know what a long day in the saddle is like. But if your road riding was four or five, with occasionally a six hour ride, you might find that touring has longer days in the saddle.
Dynohub. If you buy a bike that is off the shelf, adding a dynohub is expensive and you can add it anytime later if you want. But, if you have a bike built up (such as a Thorn), it is much cheaper to get the dynohub at the start because the dynohub wheel would only have the additional cost of the dynohub, minus the cost of the plain hub that you would not be buying. You can use a dynohub without the other electrics if you want to wait for a while until you know more about what you might like later for lighting and USB charging, thus buying a dynohub up front is not a bad idea if you do not yet know what you would use it for.
Lights, USB charging, etc. When touring I use my dynohub almost 100 percent for battery charging. If I am using my S&S coupled bike, I do not even install dyno powered lights on the bike. Daytime when touring, I have one or occasionally two rear battery powered taillights flashing. But I have never toured in a country where flashing taillights are illegal like Germany. I have a couple bikes with a dyno powered taillight, but I consider that secondary to my battery taillights because during daytime my dynohub is used for battery charging and not lighting. If I tour on one of my bikes that does not have S&S couplers, then I will have a small dynohub powered headlight, but it will get very little use on the tour.
I started the thread, link below with my general comments on what I used for charging and electrical devices on a five week tour in 2019. That tour was with my S&S coupled bike (Thorn Nomad Mk II) and it is a hassle to assemble and disassemble the bike for transport, so I do not install dyno powered lighting on the bike at all. Instead on that bike all my lighting is either AAA battery or powered from my powerbank.
http://thorncyclesforum.co.uk/index.php?topic=13696.0I have installed dyno powered lighting on a couple other bikes, including my Lynskey Backroad. I wrote up this thread recently on lighting on my randonneuring bike, this is on a different forum. When I tour on my Lynskey Backroad, the lighting would be very similar to that described in this thread. But again, mostly the dyno powered lights would be off, dynohub used for charging batteries.
https://www.bikeforums.net/electronics-lighting-gadgets/1228845-wiring-up-dyno-powered-lighting-system-usb-charger.htmlDyno powered lights, there are several brands, B&M seems to be a favorite for road riding because light beam is shaped quite well for road usage. The B&M website has photos of examples of how the headlights work at night. But some B&M headlamps have poor weatherproofing on the back and bottom of the light, tire spray can be a problem if you do not have fenders (mudguards). You do want fenders don't you?
If you get a leather saddle, the leather stain can transfer to your shorts. Decades ago all bike racers used leather saddles, they also all used black shorts. Enough said.
My favorite shoes (SPD) are no longer sold, thus can't recommend them. Your shoes that give you pain, try moving the cleats back about 5mm to 10mm towards the heel, effectively moving your shoe forward a bit. That might help. If it helps a little but not enough, move the cleats even more back.
Clothing, you are a roadie, I think you already have it figured out. But I included a few rain photos below, I prefer a good rain cover on my helmet. I also use it in cool weather to cover up the helmet vents. Sometimes I also wear an insulated ear band over my ears, you need to make sure your helmet suspension can be adjusted for anything you might wear between your head and helmet. Rain covers for your shoes are worthless unless you also have rain pants. Rain pants have to be long enough that they do not pull up above your shoe covers when you flex your knees. I use suspenders with my rain pants, that way I am not constantly pulling my rain pants back up to my waist after they slipped down. I like a good rain jacket that will work well in a campsite with a hood, but I never wear a hood when on the bike, I use a Marmot Precip jacket, I do not know if they are sold in UK or not. One of the photos, I am wearing yellow glasses in the rain. I also use a mirror attached to my helmet, I am in USA so the mirror is on the left side of helmet because that is where the traffic is. If I was in UK, I would have to re-think my mirror options. Sounds like you have lived all over the world, thus I think you have figured out everything you need to know for clothing off the bike too. Cycle clothing, especially rain clothing, you want high visibility.
I will mention one non-rain piece of clothing. A down vest packs down to almost nothing, weighs very little. I can wear that open at the front if I do not need much warmth, zip or snap it up for more warmth, and if it is quite cool out I can put a stocking cap (stored in down vest pocket) on with a rain jacket over the down vest. I take a down vest on almost all my trips.
The yellow glasses and also my sunglasses are wrap around with a reading glass bifocal insert that has a strong power (2.5 or 3.0 diopter) so that it is easy to read the map on my GPS which is close to my eyes when I mount the GPS on handlebar.
You were silent on gearing. Either that means you made a decision (earlier you leaned towards Rohloff) or it means that you have set that aside for a future decision. In a previous thread, I mentioned to you that I had three touring bikes, one Rohloff, two are 3X8 systems. Both Rohloff and derailleur are good.
You were also silent on tires. For pavement (tarmac) touring I prefer 35mm, 37mm, or 40mm wide tires. Off road, I prefer 50mm or 57mm. Get a bike with the capacity of the tire width you think you will want.
All of my 700c bikes that have fenders have toe overlap. None of my 26 inch bikes with fenders have toe overlap. I have no 650b bikes. Is toe overlap a really big deal to you, or is it only a minor inconvenience?
Hope this helps. And yes I answered some questions you did not ask.
