I'm ftm and I go to WW. I go with my mother, and she signed me up as female. But I present as male, and I think everyone there besides the one lady that weighs me sees me as male. What I found helpful was to go to an actually WW location, instead of just a meeting at a church or something where you sit in a circle and discuss. If you go to an actual WW center, you can sit in the back and listen to the meeting, and only participate when you volunteer, which may eliminate some of the anxiety with having to be misgendered. I just put my mind on my goal, and make sure I know that I have something to look forward to, even if the people think I should be looking forward to something else, such as being able to look good in a tux.
I've been going to WW for a while, and I honestly haven't heard anything about looking better in any outfits... Usually the people just weigh in and then the meeting starts. I know it's different in different places, but I've noticed that at an actual WW center, the leader is more focused on the presentation than at a meeting at a church or something. Usually, the leader presents, and along the way asks if anyone wants to share. However, I totally understand where you're coming from. I'm sorry I couldn't be more help, but I just thought I'd share.
If I actually come up with something that would HELP, instead of just sharing, I'll post again! haha