I run hot and sweat like a beast. They don't need to be bike specific (in truth I'd rather they weren't) so those a little more toward the T shirt end than the high tech string vest are preferable.
Although I've used the Howies stuff I find merino and its associated hype misplaced. It tends to get sodden, not shift wetness and loose shape. As a sleeping layer excellent but for me, as active wear, a bit rubbish. Similar experience with BAM. Also, full price Howies is a bit eye watering (£59 for their current offering
But after all those merino/ bamboo gripes I'd still like something that wasn't solely the product of an oil barrel and incorporated natural materials or at least had some component.
Short sleeve by preference.
I maybe looking for the proverbial MOAS but it's a wet rainy weekend and maybe someone fancies the challenge or to share their faves
I appreciated my comments and criticism of the above are very much IMO/E but I think they're common to the bigger, sweatier, hairier bear