Congrats on getting him to poop on the potty. In truth, don't expect too much at this point. When we were trying to train my older son, everyone (teacher and Dr's included) told us that it's closer to three for boys. They just take a little longer. We started at just over two and it was hit or miss. Jacob turned 3 and then about a week later told US he wanted to go potty and we didn't look back.
Our second son is 22 months and has shown a huge interest in it (probably due to his big brother). We brought the little potty up for him and he loves to sit on it. He hasn't gone yet, though.
We trained Jacob to sit down and pee first because he would go when he pooped. After he got the hang of it, Dad showed him how to stand and he stands now.
With Ryan (our 22M old), it's a little harder because of the way he sits down. His "little buddy" is not pointed in the toilet and if he DOES pee, it's gonna shoot straight up. So, we've been showing him to stand (like Jacob does).
Whatever works the easiest for him is the best method. Just let him take the lead and don't push it. I'm not sure about your son, but Ryan is really at a power struggle stage right now!
Good luck!