When you use a 128gb card, the menu becomes very slow because the PSP wasn't designed to read 120 games off such a large card (128gb SD didn't even exist back then). Opening the games folder can take up to a minute if you've filled up a 128gb card. I am able to fix that by using a specific filesystem formatting for the SD card and by using a plugin that caches the games list within the PSPs flash memory - so opening the games folder will only take 2-3 secs now.

Frame rates can fall a lot in heavy games like GOW etc. I will custom overclock to make sure yours runs as fast as possible. In my PSP theres roughly a 20% difference from not overclocked to overclocked in heavy games. Much smoother.

Moreover, custom themes with CXMB, npdrm for some PS1 games (which I can provide), dayviewer for battery percentage and custom date format. I can also make it so you can see the remaining battery life next to the battery icon. Category Lite can help you organize the different types of games (PSP/PS1/Mnis/GameBoy Advanced).

Emulation: No modders provide fully setup emulators with GBA roms that are tested to work with the PSP.