using the small ring is less noisy than the big one, at least on my machines. It assumes ERG mode / virtual incline though, otherwise obviously you spin out.
on alix,
BB is 10-12 eur.
crankset can be had for <40 eur w rings, i think, if you buy the cheapest, heaviest ones. Fairly good one costs 45 (crank & rings) (I recently specced that on 2 bikes for friends, perfectly legit stuff).
sensah mechanical w mechanical brakes, i've used, it works. A friend is very happy with the ltwoo R9 mechanical, hydro, i suspect they do the same, cheaper, mechanical / mechanical. If you go 10 speed or less, it gets really, really cheap, but idk if it's as good as the 11s stuff i'm talking about, i simply do not know.
11s cassette is 20-25 eur.
All shipped to Europe as of a few weeks ago.