I had written a similar program (but very barebone compared with what you've made), with Firefox only. The way I dealt with profile, is to specify the full path of the profile, rather than a name. This way, I don't have to know where Firefox is searching for profiles, and I can keep all the additional profiles in a separate directory, so they don't mix with normal profiles and don't clog up profile manager.

Yes I saw this option as well, but it seems that it's not possible for macOS