Not OP, but I have socks, underwear, and a shirt. The shirt I feel a bit meh about, because the durability hasn't been great and it was expensive (but very comfortable). Socks and underwear have been great for skiing, cycling and just days when I walk a lot. I can wear my Darn Tough socks to Disneyland in the summer and they have no smell after a day, whereas cotton socks would be very unpleasant. The ski socks are nice since as long as they're dry they're usually good to go the next day. I have gotten my merino stuff to smell eventually, but it's taken multiple days of heavy usage. And in the meantime, it's a much more comfortable to wear material.
Not OP, but I run, hike, bicycle, ski, backcountry ski, practice yoga, indoor rock climbing, and more in merino wool t-shirts, underwear, and socks.
I find Ibex makes the highest quality tees (their tencel/merino/nylon shirts are incredible for hot summers) and underwear. Icebreaker also makes a variety of good stuff.
I generally look for some amount of nylon for durability, but I have a few 100% merino shirts from icebreaker that I've worn intensively for years with no problems.
I did have some pilling issues with the merino/tencel blend from ibex which is a shame. Gorgeous fabric at first; still feels luxurious.
Laundry is a bigger deal since it's wash cold and dry flat with many of these; that can be a cost, equipment, and/or lifestyle adjustment.
I'm often able to wear the same clothes many days in a row without issue.
For pants, I prefer nylon+elastane blends, but it's hard to find. Prana used to make good things here but their Brion II line was a significant drop in quality.
Probably depends on the biodegradable fiber? Organic cotton uses a _ton_ of water. I'm not sure about viscose/rayon/tencel but I imagine it's often less water-intensive but it can be pretty chemical-intensive.
I don't know how bad nylon is to produce, but the durability it adds to clothes is probably an overall net win for the environment; compared to other plastics we consume, it does a lot of work (I've worn some items for years).
Note Prana has recycled nylon in their Brion II line, but unfortunately the quality is way worse; it pills immediately. Environmentally, I'd much rather buy non-recycled plastics that last a lot longer, so I consume/waste less overall.
Not the op, I have some winter running base layers made of meriono wool and and I swear by merino wool glove liners to wear when running outside on the cold. I don't think anything wool would be suitable for exercise when it's warm, but I've never tried it.
The merino wool mixes from REI work well in warm weather, especially when hiking where the temperature experienced can swing wildly due to sun exposure, sweat, and wind. It has the benefit of keeping warm even when wet much like wool but it breathes better.