I use BST with Capture One from Phase One on my MacBook Pro (13-inch, 2018, Four Thunderbolt 3 Ports). The app has the option to create floating windows for tools. When I create floating windows the main viewer window won't snap to the edges or a custom app window that I created for it in Catalina. This worked as expected in Mojavé. When all of the floating windows are closed, the main window snaps as expected.
Here is a beta of BetterSnapTool 1.9.1 which should ask for the new Catalina screen recording permission and work better even if you don't grant it:
https://bettertouchtool.net/releases/BetterSnapTool_1_9_1_beta.zip
Would be great if you'd test it.