Men's clothing, for a lot of things.
For some things, with tailoring to take in the sides (I'm slim).
My main problem is for long sleeved tops, plain basics for layering (my bottom layer is always short sleeved). When I size up for shoulders (or try to, given that nowhere online gives shoulder measurements), my problem still isn't that it's too wide in the torso (which can be adjusted), but that when I move my arms forward, there is a strain beneath my arms/armpit, etc. That's the back, isn't it?
I recently discovered that problem. I bought a plain long-sleeve cotton in Superdry, but while it's too loose in the waist, and the shoulders appear to fit fine, it has that problem. So not Superdry, I guess! I had a similar problem with trying a t-shirt from there once, a longer try led to shoulder discomfort.
These long-sleeved tops are one of the last things I've not been getting in the men's section, so I suppose it's just time. I have a woman's one with a little elastane in it (5%) and that provides enough of a stretch that it's okay. Jumpers seem to be fine too.
I don't often have to dress formally, so I'm generally in men's/unisex t-shirts, which in most cuts are fine for my back and shoulders. Women's tshirts are a complete write-off (too narrow in the shoulders unless huge, cap sleeves, too low neck lines, typically too short).