The problem right now is that people who say 1T sharingan can't use genjutsu or can't copy ninjutsu/taijutsu, forget the longest person we've seen with 1T sharingan was sasuke. Now let us re-establish who sasuke used the sharingan on. Haku was the only person we've seen 1T sharingan sasuke fight. Haku has a kekkai genkai, which means its not possible to copy. Also, Haku was jumping from mirror to mirror so precog wasn't possible since you can't see the muscle movement of Haku. One last thing to add, we did not see sasuke use sharingan genjutsu until part 2 so this makes it impossible to determine if a higher tomoe is needed or if you only need to train at genjutsu. Just to recap briefly Haku is the only fight we see with a ninja who has a 1T sharingan.
Moving on to another point, I'm also seeing talks about how could sarada copy a technique that requires kiba. The lightning fang Kiba has been imbued with lightning. This means that the blade itself doesn't give the user techniques outside of their jutsu arsenal. Of course, if someone has a databook entry on lightning fang kiba that contradicts this then sarada would be unable to use the 3 lightning element jutsus acquired from Buntan.