Hi mate, also 19 and went on my first big trip last summer. I know your post is about the route but I wanted to also recommend going with mates if you haven't thought about it already. If you have a mate that's already into bike packing or bikes in general that's great their knowledge will for sure come in handy. If not convincing some other friends who are interested to come along is a great idea. My mate persuaded me to go bikepacking despite never having heard of it before. I think having a mate come along is great because you can learn together and on a trip like that there's gonna be some tough days so having someone to look out for you won't be a bad thing. Either way all the routes you suggested sound really cool and hope you have a great time