I'm new to Eurorack and i'm planning to buy a 6U case 84HP, however all the planned modules that I've put here in the grid have exceeded 84hp already, so i was just wondering if that would be a problem if were to do it for real. Thanks.

Well, collected modular wisdom says whatever your rack size, it will be too small soon. Only question is how soon.

Amen. I have found out about the HP size thing. It doesn't matter as long as it fits, and yes, how soon will it be. I fear for GAS taking over.

I am convinced that 6U/84HP is a good size but you have to be a pro planner to make it count.
9U is the gold standard and everything larger 9U gets to a compulsive problem.

Not a bad idea, to start at 3U 104hp I guess...