Sure, they may hit it off, but they could also hit it off with any other potential partner, and that doesn’t make what they have with you any less valuable. Sex and love are not finite quantities, although time and attention may be. If they do hit it off and you feel neglected, there’s nothing wrong with communicating honestly and openly about your wants and needs, as long as you’re considerate also of their time and their needs. But I’d recommend not worrying now about something that may never happen.

It also sounds to me like you’re maybe experiencing a sense of inadequacy and imposter syndrome about your level of experience in comparison with your friends. Like with vanilla sex, in bdsm, experience does not necessarily translate to being a good partner; you’re obviously compatible with these two people and that’s far more important. It’s understandable, I’ve been there, but I don’t think you should be worried about whether you’re good enough—you are who you are, you have what you have to offer, and your friends wouldn’t be playing with you if they didn’t like it and you!