as long as the jam Rules allow Teams (or doesn't disallow them), it's completely proper for you to offer your skills and interest within a jam's Community similar to what you've posted here. also, many jams have a Discord server that will generally include a "looking for teammates" channel where you can offer your services or connect with others looking for contributors such as yourself. and, speaking of Discord, consider joining the Itch.io server if you haven't already. you'll find a looking for team channel, there, as well.

and, while you are free to Join a jam, only one member of a team submits the project from their account. with that, it would be proper for your username (and link to your profile) to be included on the project's page/credit be given for your contribution which i recommend you build up your profile to showcase a little of what you do. perhaps a spotify or youtube preview of music you've made, etc, would be ideal. or, if you have a few tunes that you'd like to make available already, consider making a project page and posting them there.

re: WAV files specifically, i don't know about other devs but WAV files are generally overkill, to me, especially for a Jam game (i dont like huge files/packages when they dont have to be huge). i prefer .ogg myself but that is something you can discuss with any dev/team you might collaborate with.

i hope that helps get you started here. good luck and find some fun :)