I really like the look of the Borns, and I'm not a mule-lover at all. It sounds like all three mules could be good work shoes for you and the mule style suits your climate and your feet. It sounds like you're not chasing a trend so much as taking advantage of a style that suits you -- it is a good time to stock up on mules if they're your thing!
Definitely prefer the Allbirds over the Propets. If you end up loving the mesh version for summer wear, you can always duplicate later in a different colour or style, or get the wool version for cooler weather.