--- 1U Row---
The 1U - makes sense to me, and without QoP drum module, the midi controls in there should be more then enough to start. Saves 3U space.

personally I think 1u makes little, to no, sense whatsoever... the cost of the 1u row is the same as for a 3u row, or in some cases more, I'd much rather buy 2 tiptop mantis cases than 1 of the intellijel 7u cases... and you can get much much more functionality in a 3u row than in a 1u row...

---Audio Row---
Also about tuning the oscillators, I guess I would need to tune with an external module or scope?

a free phone app or a guitar tuner pedal (plus appropriate cable) or your DAW (if you have one) will work for tuning!!!

--- Good starting build---
In the context of:
1) What I was willing to spend originally with endorpin.es setup
2) Assuming I minimally start with 1x single 258T, 1x Folder, and the 1U utilities
3) And I currently have PNW, Maths, 1x Veils, and Beads already

What other modules would you suggest to start with right away, and maybe a couple additional modules after? Also not to many modules, to get overwhelmed :0

none - just grab the vco and folder (& the utilities) and see where you are - learn these modules inside and out and then start working out what you are reaching for - and then slowly add modules that add those functions

"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia

Utility modules are the dull polish that makes the shiny modules actually shine!!!

sound sources < sound modifiers < modulation sources < utilities