Always eat your greens!
Performance and how configurable things are, plus ease of use.
For instance, my default router/modem device from my ISP was super clunky and confusing. I needed to set up some custom port forwarding and firewall rules. The aftermarket router I bought was faster, had way better wireless coverage, and the UI was so much easier to set up the configs I needed.
So it’s up to you, from what you said, seems like you probably would be good with the default from your ISP.
If you’re on a budget, check out X99 socket Xeons. You can pick up Mobos and chips for super cheap. 10+ core hyper-threaded Xeons with solid clocks and a motherboard for 120-180 bucks total. Support 64 GB of RAM, more if you have a proper server board.
For transcoding, depending on the codec, dedicated GPU is best.
I’m not sure about Plex, but I know on Jellyfin, the new Intel Arc GPUs are really great for encoding, not too expensive for the lower end cards either, and low profile options for smaller rack cases.
XCP-ng or Proxmox if you need a bare metal hypervisor. Both open source, powerful, mature, and have large communities with lots of helpful documentation.
I think you can migrate ESXi VMs directly to XCP-ng. I have moved onto it about 6 months ago and it has been solid. Steep learning curve, but really great once you get the hang of it, and enterprise grade if you need stuff like HA clustering and complex virtual networking solutions.
I’ve been thinking of using Linkwarden for a while now. As my computer usage spreads across more and more devices, having a single place to go for all my bookmarks would be fantastic.