Hello,
I wear the Desoto wing skin cooler top that goes across the shoulders and back and down the arms. I wear this not so much for the cooling aspects but for the fact that it gives me sun protection. I find that it will only cool me if I pour water on it, which is what I think it is designed for. It will not make you too cold if you wear it on the bike if anything, the long sleeves will keep you warm if it is cold outside. If I wear it when it is hot, it will actually make me hotter unless I pour water on it. I would not wear it under a wetsuit. It is very fitted. I have an extra small and I’m tiny and it is very fitted. Hope this helps!