Because I stream all run attempts on Twitch/YouTube, they usually contain webcam footage. Will the camera make the run any less valid? And does camera position matter (as long as it isn't blocking UI)?

You just answered your own question [quote=ActualArcher]as long as it isn't blocking UI[/quote] So, no, generally, it doesn't make your run any less valid, the position shouldn't matter, and yes, you can use one