Kap, Do the PIA config files all use the same ports? I've never heard of a blank or un-configured OpenVPN client on an Asus router to auto-populate the next unused OpenVPN client with a previous client's information. PIA works well for some folks, but didn't for us. They're in the process supposedly, of re-writing their software with signatures, but I never got as far as being comfortable enough with their code to attempt to try it on our router. The PIA windows client was not well behaved, and I didn't have time to spend with unsigned software. Some justify having unsigned software as being too expensive, but crying poverty when PIA has so many users isn't convincing to me. To each his/her own.
In your case, it's tough to make a call on user error since there's no background on how complex your LAN or router setup is, if it's due to user error, or a problem with the configs. As you're discovering, this is a very involved subject and takes a lot of time and patience to learn the ropes. Only one seemingly insignificant mistake can bork your config or make the router unusable. V382 is a whole new level of code and complexity and will be a while before it all shakes down, and PIA doesn't usually keep up with Merlin as much as some providers. Nord usually has good setup guides and though it takes a day for them to get back to you, they seem helpful enough.
It might be a bit inconvenient for you, but better to eliminate the chance of this being user or PIA error now, since it's not going well. If it were my situation, I'd download the Nord configs and setup guides you need and make sure you take a screen grab of the important pages/settings on their site if you need to refer to them. Then use the default button at the bottom of each OpenVPN client window (may vary with 382), and zero out each OpenVPN config, saving/applying each time. Then reboot the router, log back in and see if those configs are actually gone. If they are, then you can upload and save one Nord config saving each change as you go, then if that goes well, try one PIA, if you need it. If Nord doesn't give you any trouble, maybe those are the configs you want to keep.
I'd suggest not configuring all of the tunnels at once, instead, either log out or reboot after each config is entered. The logic being, if the config is still there and works each time, you'll probably be getting more experience and be able to identify where you might be going wrong; if you're going wrong. If all of the Nord configs work out and operate as you need them to, then try a single PIA config, apple it, log out, back in, then see if everything is in place. If so, try each config out, before proceeding.
We normally run two configs at any one time but can easily get by with one. It's easy enough to log in when you need to turn on the tunnel and takes up less resources in the router if you don't need the tunnel. If you have a port conflict whether it's with PIA or Nord config, it will probably give you a headache and/or not work, or work poorly as it is presently. You may have better luck while you're testing if you don't have the configs turn on automatically, instead, turn on one, see how that goes, then if you need the second, turn it on afterwards. All things in moderation until it's all working well. Hope this helps, Cheers.