Probably some other QoL touches that I'm forgetting. You can talk to the gym guides for a full party heal mid-gym instead of having to leave for the Pokecenter, the game no longer asks for confirmation when trying to use an HM by pressing A while facing something that an HM can be used on, you start the game with a bike, etc. including new items Common Candy and Uncommon Candy which give a flat amount of EXP to help the player keep up with Johto's much steeper level curve. It's not an overly ambitious romhack, the main idea was just to rebalance the Kanto postgame with a sledgehammer by making it so that everyone there rocks level 100 Pokemon (with few exceptions), then I rebalanced Johto to accomodate this and prepare the player so they aren't blindsided by Kanto.
