I’ve never attempted anything like this before…but
1. Yes, think the head from RCT woul work best…easier to form the mouth, easier to attach to the cake..especially can be hidden by the t- shirt
2. I also agree with modeling chocolate, it is more forgiving. Or you could also do a 60/40 fondant and modeling chocolate ….that could work too…
Creativity is God's gift to us. Using our creativity is our gift back to God. Clarky's Cakes 😎