I have been using a bottom mounted radiator with my Evolv Shift for over two years and its still running fine
It will probably be fine to run a bottom rad in an NR200 but dont expect the aio to last long, budget replacing it every 2-3 years. I want to replace mine but the Corsair H80i is not available anywhere.
Or you can do a custom loop with a Barrow pump block; but that would probably cost 12K excluding fans.
The new MSI liquid AIOs use a pump mounted in the radiator. Based on reviews, the performance is slightly less than Asetek based coolers such by NZXT or Corsair. That should be completely fine being bottom mounted.
Meron dito naka Ncase M1 using 3700X with AIO. Anong idle temp and load temp niyo? Games or benchmark tools used. Salamat in advance. Gusto ko sana i-check kung tama lang ba nakukuha kong temps sa akin.