I would be pleased to help with questions about blades. If you would like to call, we are open Monday through Friday 11 a. t 4 pm Eastern time. Or click on the link below my signature.
I think your question was mechanical. As a dealer for Pegas, most of the sales are the 21". I sold one 30" to Rodney here on the forum. I find very few problems with either size.
Mighty fine cutting. I call this portrait as it is a picture of something, could be anything. As for framing, make the project the size of standard fraames such as 11" x 14".