Here is my Nomad Mk3 size 540L with the Ortlieb Frame Pack in its 6L version. (
link to bigger version of photo).
I got the Ortlieb bag because I wanted a roll-top bag. Frame bags with zippers are infamous for breaking.
As one can see, there is room left underneath the bag for mounting my pump.
I don’t use the triangle for water bottles. Instead, I find that feed bags are a superior solution for carrying water bottles. The Decathlon feed bag is cheap, but reliable for the long term, and it can fit even a Nalgene bottle.