I have to be honest with you DR, I don't choose blades by their tpi or thickness. I choose blades by their universal number, such as a #7 or a #2 or a #2/0. As for speed, that is up to you. I teach my students to start at about 50%. If you think the cutting is going to slow, speed it up. If you can't stay on the line, slow it down. Trying to formulize your cutting will drive you crazy! If it works for you, do it!