Do you have a major ISP that gives you trouble downloading torrents? (and are you paying for a VPN already if that’s the case?) Do you have low upload speed and therefore contribute little to torrent sharing?

If yes to any then answer is probably. If you already pay for a VPN then answer is very probably because you can pay a similar price and not need the VPN.

Depends on the ROM you want but Google/Oneplus devices are very commonly supported and easily unlocked. OnePlus isn’t up to it’s current iteration on some major roms but Google pixel 7 line works with lots of the popular ones (specifically: lineage, paranoidandroid, evolutionx).

I’d choose what ROM you want check supported devices to make sure they have one modern enough for you then decide based on that.

Probably goes without saying but avoid carrier phones as they are generally harder to unlock the bootloader or sometimes impossible.