I just made it back to my development computer and changed the Raspberry Pi configuration changes to see the change in performance.
Following the directions at Raspberry Connect , the mesa-utils were installed by default on my Raspberry Pi 3 B+. I tried both Full KMS and Fake KMS settings and here are the results:
Setting Frames Per Second
Default (No Move, Xojo) 5-7
Fake KMS (GlxGears) 60
Fake KMS (Move Mouse, Xojo) 6
Fake KMS (No Move, Xojo) 12
Full KMS (GlxGears) 60
Full KMS (Mouse Move, Xojo) 6
Full KMS (No Move, Xojo) 12
The Xojo program was just a cube rotating at full screen size. There was no texture, and no video running.
Note: When I move the mouse over the OpenGLSurface control, then the frames per second decreases. There is a similar anomaly with OpenGLSurface on Windows.