I'm not sure if this is the same issue as you have but this what I've noticed.
When a transparent Label or ImageButton, and an Image paints it can be slow at times
What I see is a white flash. This is when having a dark background.
I try to limit the use of any of those controls, and favor DrawString with a calculation to center it, over a Label.
And DrawImage vs. An Image control.
I havent experimented with AutoScale yet to see if DrawString would still be centered, or as close as it can be.
This is what I use for the X location when centering the Date on a form.
It is very close and used on QVGA.
(Form1.Width/2)- (StrLength(Date(Now))*3)