Ok about the slow down speed, I was wondering why because most of the wipes don’t have this slower motion. So I guess it’s fine !
It can be tough when you want to use a wipe in a shot that wasn’t rendered or filmed for one! The amount of time between the end of the action and when they cut the shot can be too short to work with. So, sometimes you need to slow down or loop something if you want to build a wipe.
In Premeire (and probably other packages), you can make it look a little better by turning on Frameblending for the slowdown (interpolation).