Transparency is a video effect available in Windows 10 and makes the BLACK color completely transparent in the logo and in titles and video texts. Moreover it is possible to adjust the transparency of all the other colors in value from 0 (invisible to 255 completely visible), recommended value about 200.
Here is an example:
this is a MB SOFT logo with a completely BLACK RGB background (0,0,0)
when transparency is active, it's displayed like this:
The same thing applies to titles and video text.
ATTENTION: if TRANSPARENCY is activated in Configuration\Video\Options1 you must set OBS Studio to use the capture method: "Windows Graphics":