If you can make them choose (and explain what's going on) sure. But if not, just put them on semi-random list and but let them change later. The most important part is to get them in, and help them setup when they are ready.
so when you onboard a user on a client you should publish their relays of choice? on sign up? say a set on onboarding relays? that they can later set-up add/remove in relay settings?? asking for my app https://github.com/turizspace/hisa/releases using multiple NIPs 28/99/17
Discussion
On that note how does amerthyst know what my relays even are? I assume its a hardcoded bootstrap? Would make sense if that can be configured on first boot and is then cached.