i will give u some lessons
recently brand had bad matchups that were horrible because of enemies pushing him hard and forcing him to waste mana
riot gave him a new passive that gives him mana when he kills a unit affected by blaze
to balance matchups u need creative ideas that dont affect the situations outside those matchups alot
that change worked
riot changed graves hp regen to bring him up a bit
it didnt change anything because graves barely gets hit in the jungle
dont change stats that dont matter for the champion ur changing
that is a medium fail in the way where they have to give it another shot on balancing him until the next patch wich will take some time to come out
riot buffed ornn knock up hitbox on e it helps him on hitting e wich he rarely hit in the past
now ornn is a viable pick that isnt op or weak a really good change
some champions will become op if u straight out increase their defense or damage even if by a bit and u need ways to make their current options more reliable
riot didn't change janna's shield health for a wile instead they nerfed the other parts of her kit that dont matter
now riot fails each patch to make janna not op and she keeps her spot as one of the best supports
think about what ur changes will impact and if that does actually matter