Given how we see him pull/yank/grab Tifa throughout the games, including pulling her into a hug and following it up with him kissing her, I absolutely believe Cloud is the dom in the bedroom.
Cloud is pretty and Tifa is badass and a physical fighter so I think a lot of people have fun with the idea that Cloud might be the sub, but thats the thing… He isn’t with her. She brings out that more dominant side of him.
I also agree that Cloud is much more eager to eat out Tifa than Tifa can keep up with desire to suck him off. But I also can’t imagine Cloud really needs to ask.
I also imagine Tifa masturbates a ton when Cloud is out on longer deliveries.