In general, the stability of custom roms and random bugs you encounter may be more than with officially supported operating systems. It might be totally fine, but if you’re the only person who has encountered a random bug and no community dev is interested in fixing it right now, it might stick around for a while.
If it’s your only device and you need it to work, I might recommend trying it out on a secondary device first to make sure it works for what you need.
Philosophically I agree and am aligned with open source and free apps, but the reality is I don’t have the time or patience at this time in my life to deal with that kind of thing. Your calculus might be different though.
Also worth noting that meds will work differently depending on how old you are. A med that was to much as a kid might work well for an adult. The unfortunate thing about focus meds like this is that it’s ultimately self-report, so I don’t know if there’s going to be a test for you to know if things are working properly. Personally I find it easier to start tasks and find myself procrastinating less. Not to say it goes away, it’s just easier to get over that initial inertia while on meds.
The doctor is going to try to get you to a dose that gets you your intended effect (being able to function) while minimizing side effects. Try keeping a note of how you feel, what your thoughts are, how easy it is to do the things you need to do to function, etc. on different dosages to see if you can look back and see patterns. It might not be obvious at the time but might become more obvious in retrospect.