I can’t jump in for everything related to NAS, Yunohost or RAID5.
However, If you wan’t to host the arr stack with jellyfin or other media server, you probably need something to encode on the fly (some kind of GPU).
CPU encoding is superior but slower. Also this would leave your server CPU for other tasks more important. Encoding is very demanding and could bottleneck your whole server if you only rely on the CPU to do the heavy lifting and share your media server with family members.
Oh yeah so only couch watching :) !