Quick Question, What can you consider a yumeship?

Hiii, I really wanna try out to yumeship and there's this character I've been obsessed with. Does my yumeship self have to look like me? I was planning to turn my oc x canon to a yumeship but keep her looks & age in. Idk if there's like a rule that the yumeship has to look and has the same age as you so that's why i wanted to ask it.

I'm just really curious and wanted to get this question clear before i can decide on my sona. Thank you!