I can only speak for myself, anecdotally, as no two brains are quite alike.

I was a very intelligent, effeminate child with delayed onset puberty (among other things). I had constructed my own shortwave radio equipment, and built little science fair projects like an organic dye pulsed LASER, the ever-popular Tesla coil, and an ECG machine with a CRT display. I was very good at math, including geometry and differential equations.
Then I was helped with testosterone injections. Dad said they were "vitamin shots, so you'll grow up right." Grades dropped from As to Ds, my attention span vanished, and I couldn't think straight. A couple years later, I struggled in college, eventually dropping out for military service. I seemed to get better as time passed, and I finished my physics degree in the service.
Now, at age 62, I've started HRT. About 3 weeks after I started an anti-androgen, spironolactone, I started to have flashes of insight that greatly sped up work on some hobby electronics projects. 4 weeks after starting HRT my testosterone had been cut over half, and was at the minimum normal for a cismale. The last week or so I feel mentally like I'm firing on all cylinders, preparing a presentation on a technical topic that I'm giving later today.
My ability to concentrate is greatly improved. I've referred to this effect in the past as 'the noise in my head' going away. Not an auditory hallucination, but the buzz of distracting little impulses of mental junk.
My old therapist mentioned something to me one day that I thought was very interesting, regarding self-confidence. I mentioned that I always felt that, in spite of being a top performer and well-regarded individual in my professional field, I always felt deep inside that I was somehow a fraud, and would somehow be 'found out'. I worried that I might have done things that deliberately damaged my career and life, a sort of self-sabotage, and that perhaps this 'Trans' thing was just more self-sabotage.
Nope. He explained that by hiding my nature for so long behind the false front of a male persona, that I was used to hiding and having a damaging secret, and was generalizing that 'fear of discovery' beyond my actual secrets and across my whole life. He said that this 'Imposter Syndrome'
https://en.m.wikipedia.org/wiki/Impostor_syndrome was actually common among transgender persons.