Does low cpu mode interfere with that at all or does it just make the bots frames loweR?

Low CPU does in fact interfere with the bot's performance so yes you will get a lower xp rate.

Half the times the scripts wont even function with a low frame rate.

It depends on what you are doing. If combat, then the script might do some misclicks due to lag and a moving target. If woodcutting or fishing, I see no performance difference

I remember on a different bot I used to use, you could minimise to the task bar which reduced CPU and also you could remove the interface, leaving it just black and that worked too but didn't decrease the FPS or XP/ph

Faster fps = faster xp. Had to clean my computer to get faster xp.