I was wondering why there isn't a sub-category for each difficulty for every heist and full-game. Speedrunning something on Easy and Overkill completely changes the cards on the table.

There is now. :)

You're always the best! I might return on PDTH for some speedruns, I find a lot of fun and satisfaction by doing them lately, I think it adds a new meaning to the game. I tried on PD2, but it's a RNG fest. Welcome back PDTH!