I ran on a Pi 4, but switched to a PC for jellyfin. The pi can’t transcode for shit. It was slow to boot and slow over SSH.
Look for a NUC - they’re designed for desktop use, so they have more poke than a Pi. The N6005 CPU is a good choice, the N5105 is ok. These are x64, so you’ll have the widest range of packages. 4GB will do, if its upgradeable later. NUCs usually take SODIMMs, which you can pick up on ebay for peanuts.
Bear in mind that network chipset will be your bottleneck in some use cases. If it has a “gigabit port” but only a cheap chipset, and you use it as a router, you might max out at ADSL speeds… in that case you’ll wish you’d gone for a box designed for soft routing, which are a fair bit pricier.