Ok in that case. The goal is to use a cipher suite that works well on your device that is still secure. AES is accelerated on most processors these days. But you’ll want to confirm that by looking up your specific cpu (both host and client machines!) and checking for AES acceleration.
AES-128-GCM would be my suggestion.
UDP mode provides less overhead, so it should be faster for you.
Alternatively you could use IPsec instead of openvpn but that’s a chore to configure. But it has the benefit of being free and being natively supported by many devices.
You would still want to configure an appropriate cipher suite that’s fast and secure.
You mentioned that your cpu is getting maxed out on wireguard. That makes a lot of sense since it’s generally not hardware accelerated, old low end CPUs could struggle here.
What choices do you have for protocols with your VPN software?
Well at the end of the day it’s just all wire, a knife and a soldering iron you can change them out however you like. But I’m assuming that’s not what you meant.
There are adapters, startech makes a bunch of different kinds. So you could use a USB adapter over the USB extension cable.
Historically people would use stereo wire for stuff like that.
koboldcpp works fairly well. There’s lots of different models to try and the choice depends a fair bit on your computer specs and what you wanna do with it. github.com/LostRuins/koboldcpp