Yeah! It's super fun to max upgrade a powerup to a God-like tier. I find myself doing it when playtesting the game just for fun haha. It's very overpowered, but that's part of the fun. It gives the player a real damage spike.
And yes! The hearts are percentile now. It's been kind of a pain in the ass to animate, but it basically serves as a healthbar under the hood (player has 100 health = 5 hearts) and they move up and down in percentages just like in zelda. I find this works better because it's like having those little subdivisions in a health bar like in league of legends, which suggests to player at what point they should start caring about their health.
Thanks dude I can't wait to have you try it out :D