Having not actually seen the Wan-Bissaka handball, but taking your word for it that it is virtually the same as the Grealish incident, I can still tell you what the difference is. As said above, the on field decision. Grealish's was not clear and obvious enough to overrule an on field decision of no penalty, Wan Bissakas was (presumably) not clearly and obviously not a handball enough to overrule the on field decision of penalty. They could be identical incidents and have different outcomes based on the on field decision. Whether you agree with that or you don't, that's the way it works.
With regards to the offside situation, I get bored to tears of people moaning about this. Whether a player is in an offside position or not at the time when a ball is played is NOT subjective, it is a matter or fact, black and white. Whether that be by a toenail or a yard, it's still offside. People wanted technology, and this is the sort of thing that the technology will do.
Changing the offside law won't change that either, as even if we change it to the daylight rule, people would bemoan 'there was only the slightest spec of daylight'.
I've seen barmy comments of 'but if it's that close, they shouldn't get involved' - well where are we going to draw the line then? and 'VAR has robbed coventry of one of the greatest moments in FA Cup history' - well unfortunately sentiment doesn't come in to it either.