In a large envelope but they are in a plastic for bigger seeds you just have to write fragile or do not bend or hand scan. I have yet to hear a problem about them. And I've had no issue with people who have sent me seeds the same way.
The Sugar snap peas I grow in a raised garden box. I use to posts on each side and use twine to strip up 3 lines between the poles for them to grab ahold of. They grow like vines. It needs some support or they will just fall over. Full sun plant after last frost. Soil needs 1-2 in water week. I use organic potting soil with compost and banana peels and used coffee beans grinds... just make sure they are used coffee grinds.