OP, your fear is not irrational. Acne is one of the side effects on the list that I stared at the longest, because it causes a lot of stress all on its own, not to mention on top of a long list of other things related to dysphoria and transition. I'd say, just figure out a game plan to tackle it and prepare for the worst.
When I started on T, I was dreading it coming up. I didn't have bad acne through the first round of puberty, but I've also read about people whose faces exploded despite not experiencing it ever in the past. It just depends. So far, I'm good, but my doctor put me on half the dosage of T to start. Recently, she increased the dosage, but stated that if I haven't experienced a lot of acne so far, that my chances of it not occurring is good, but by increasing the dosage, I'm increasing the risk of side effects. Talk to the endo/derma/doctor if you want to test out the different paths.
While it's not bad, I've stopped shaving my chin as it seems that the razor is irritating that area and causing it to break out more.