I've been curious for a while, can you enter a ranked match transformed ( Kaioken, Ssj) or do you have to transform during the battle?

you can enter transformed, but the transformation will be taken off before match starts. so yes to both, but if you enter with it on, it will be taken off automatically

in order to fight in rank with transformation, you have to cast it at beginning of round.
be warned though, the transformation will be taken off at the end of the round you used it, so it acts exactly like buffs do in rank, except much longer cd on transformations. hope I helped.

ok T%hanks cause I always wonder why i dont see many super saiyans in ranked.