do i have to pause to change fps? i know i can use rtss to cap my framerate but it doesnt explicitly say i can change fps with it too and just wanted to make sure before i submit an actual run

Since the changing of FPS is possible through the in-game settings, only the in-game settings are allowed to change/cap the FPS. You can have a 3rd party programm running to Display your FPS during the run (Rivertuner, Steamoverlay, Nvidia, ...) but the change of FPS is only allowed in-game :)