Matt,
Some thoughts on your question about climbs:
What is the most efficient way to climb a hill?
Or rather, the way to express the least amount of energy?
From my experience, another e-word comes into play: enjoyment.
Your followup implicitly takes you there:
I imagine a slow accent, arriving at the top at a very slow speed. And then coasting down.
I had plenty of time to ponder All This in the summer of 2016, on my ride through the Rockies & Cascadia to the western ocean, here:
https://www.cycleblaze.com/journals/rockies/That tour was full of long climbs and long descents: the high passes required three hours' climb or more to cover the 25 - 35 or so kms, depending on stops and pauses for one thing and another, bears 'n' such. Nearing 70 at the time, I had no option but to climb in my lower gears, although I used 1st only four times in the entire tour. But, I made a virtue out of necessity, as one does, and decided that
the best way up these hills was slowly and deliberately. (I did met a couple of guys doing it another way, lightly loaded, headin' for the next hard accommodation 160+ kms away, with a damn great mountain in between...)
Now I know that popping over to the Rockies to try all this stuff isn't the easiest/quickest option available to you, but there is another one, a little closer geographically and culturally. Place called Nova Scotia, not so different from Old Scotland, complete with hills, horizontal rain off the North Atlantic in June, that sort of thing. I had a tour planned there for the summer of 2020, at the heart of which was the Cabot Trail around & over Cape Breton, but The Great COVIDian Thing spiked that. Depending on how my spiffy new hips perform, I might have another run at that a couple of summers hence. Interested? Send me a PM if so.
Cheers, John