kokot, thanks for the congrats and sorry for the bug. I'll follow up on the bug report.
Vuo asks macOS to use whichever GPU macOS thinks is the best in the system. Sounds like your macOS is not deciding correctly for some reason.
There is currently no way to override that decision in Vuo, but maybe printing some debug info would give you a hint of how you might reconfigure your system to make it work better. You can do so using
defaults write org.vuo.Editor debug -boolean true, as I described in a comment above. (Or if you don't want to sort through the many Console messages from your entire system, you can export the composition to app and run the app in Terminal with debug info enabled, giving you the output from your composition only.)