Honestly, I just use wg-quick to connect to VPNs, and I tested out ProtonVPN and it worked fine with it. I even set up my router to connect to ProtonVPN, so I could have a wifi network that’s always connected to their VPN.
But I’d really rather not have the same company host my VPN, email, and other stuff, I’d prefer to separate them a bit so no one company has a lot of my data. And something like a VPN really doesn’t benefit from bundling anyway, unless it’s bundled with a browser or something a la Mozilla VPN.