I don't think I had any issues with OBS Studio myself, but I do share that same issue with that streamlabs version.
And while window capture does work, it however doesn't seem to be a way to have it transparent like you can with the game capture option.
However there are the filter options, like chroma key, that I can add to the window capture. Just need to make sure your image has a decently cleaned cut edge to reduce bleed through