Hello Xavier,
Welcome to the AusBonsai Forum, and I hope you'll be a frequent visitor. But providing you with a compact course in styling, incl. a virtual design for both maples, that's not so simple! Also, you are about to enter Winter and in your part of the world cutting and pruning maples now may not be the thing to do. I would suggest you join a bonsai club in Seattle and visit also the Internet Bonsai Club. Use the Winter to study bonsai and plan which species of trees you'd like to acquire in the future. By the way, "red and green maples" doesn't tell us much, there are many kinds of each and they vary widely in the way they grow.
Here are some useful websites of the American Bonsai Society, Directory of clubs, IBC
...
Best wishes,
Lisa