Growrilla single pot DWC or Oxy ring

I'd be more worried about the smells vs the noise. your growing weed in a shared storage space, they are going to smell it.

I’ve tried both systems before bro both are solid, but the Oxy Ring runs a bit quieter and is easier to maintain long-term. The DWC gives slightly faster growth if everything’s dialed in perfectly, but it needs more attention (pH swings, cleaning, etc). For nutes, I’d start simple something like Advanced Nutrients pH Perfect or GHE Flora Series works great. Just make sure to clean with hydrogen peroxide between runs to keep roots healthy

I would go for the without the ring if you want silent the sound of trickling water might bring unwanted attention, there not loud just as loud as the air pump but there's ways to quiet those up or invest in a silent pump.. I like to use canna aqua range nice and clean.. I also use silver bullets this will stop root rot and slimy scale build up giving easier cleaning.. After a full cycle you can clean them out easy enough with a diluted bleach as long as you rinse propetly.. Hope that answers questions 1 to 4.. Good luck growmie