Depending on how well you know your way around, my recommendation is to not use the Ansible setup but instead treat it as documentation while doing things your way. It has quite a bit of strange stuff going on (postfix? two nginx installs with only one being in a container?) and seems to be missing important things such as SSH hardening. It also assumes it'll be the only thing running in your server just in general (horrible yet common practice, unfortunately) so if you have anything set up it may or may not clobber over it to do things it's own way, and end up breaking something.

Also, can you log in to wefwef through your instance, or how do you access everything, specifically on mobile?

I haven't tried wefwef in particular but all native apps I tried work just fine. An issue I can see cropping up from wefwef is that Lemmy's CORS policies are way too restrictive by default. No idea if they do any kind of proxying to get around that but that would be the main issue I'd imagine.