I have over 300 videos on MV, and only 5 of those are boy/girl vids (4 bjs, 1 sex vid), and while those do sell, most of what I earn is from solo vids and I definitely wouldn't need those bg vids to be successful there. My username is veggiebabyy on MV as well. Feel free to check out my page to get an idea of what I post. I think it may help you to scroll back to some of my older videos and see the kinds of things I was posting when I first started. When you're new to something, your quality won't be as high as someone who's been doing it for a while, and that's okay! Don't worry about it too much. Film some videos, post them, and see what happens.
As for what sells for me, people like schoolgirl outfits, JOIs, leggings, breeding... stuff that I would consider fairly vanilla. I do occasionally post more fetishy stuff (like armpits and belly buttons) and that stuff usually does pretty well, too. I post on C4S, Manyvids, IWC, and MFC Share, and in my experience, manyvids is the most accepting of a wide variety of content and is the most worth it of all those sites.
Basically, stop worrying about it and just post some stuff. You'll never figure out what works for you if you never try. Throw stuff at the wall and see what sticks.
Quick edit: I'm also on MFC (Started on MFC in August 2019, joined MV at the end of 2019), and I also had a lot of guys asking about boy/girl content in the beginning. That has died down since I've become more established as a solo model. I have those couple bg videos there for the people who really want to see it, but most people prefer my solo stuff. I think as you establish yourself and put out more content, people learn what to expect from you and will stop asking for other stuff—mostly. I still sometimes get asked for really off-the-wall stuff (girl/girl? vomit? raceplay? have you ever seen that from me???), but I think that'll happen no matter what.