Old trick... For movement, you only need to redraw the things that changed. Though RenPy doesn't have a back-buffer which you have access to... You can draw all static items, which everything sits on-top of or can only be walked in front of, first. (All on one layer.)
Then, draw the the rest on the second layer, in z-order, devoid of characters. That makes less to re-draw, as the character moves.