Open port security, ExpressVPN and Remote Desktop - setting up a remote access to my desktop PC or LAN

I have a desktop pc at home that I would like to access from my laptop, outside my LAN. I am doing this more for the fun/learning of it than out of necessity so "unusual" or "extra-step" solutions are fine by me. I have ExpressVPN and first I was just gonna see if my router would support setting it up on it and then connect my LAN via that, but I contacted them and they do not support port forwarding/remote access. Then, for now, I am not gonna learn to set up my own VPN but just test to use Remote Desktop Protocol and open one of the router ports(port forwarding right?) and then connect to my PC like that.

I have two questions regarding this:

If my PC is always connected to ExpressVPN would that somehow disturb this plan of mine? I connect to the open port on the router and it would still be able to forward me to the PC?

When/if a hacker is searching for an open port and finds mine how can he possibly abuse it and can I protect it somehow? Can I put a password to an open port or?

As you have probably understood I have a very limited understanding but I am trying to read what I can and do some "experimenting". Thanks.