I use Bazarr alongside sonarr and radarr and it works pretty darn well

I’m happy with the stock, but they do at least make it easy to swap firmware.

For router recommendations, I’d go with a Gl-inet router. they run OpenWRT out of box and smacked the hell out of my previous Netgear gaming router in both wireless range and stability, especially on 5GHz. I have the Flint 2 right now and I believe they just released the Flint 3 but the one I have is more than enough for my home network.

for Jellyfin specifically, get yourself a cheap x86_64 PC and cheap or used graphics card. (or a cpu with integrated graphics)

for example, my jellyfin is running on an AMD FX-6xxx processor and a GTX 670 just fine.

the raspberry pi will work for Jellyfin as long as you don’t have any transcoding to do, but the minute you need transcoding you’ll need a GPU or good encoder/decoder chip.