TrueNAS scale helps a lot, as it makes many popular apps just a few clicks away. Or for more power-users, stuff like the linux cockpit also really helps.
To directly answer your questions…
Assuming your old router might survive as an access point, maybe consider a Protectli FW2B? https://protectli.com/product-comparison/
Double-twist-back: it’s not under a special TLD, so you can transfer it to another registrar.