Shoulder epaulets are best although cuffs are simple and visible. I'd go for both. For some reason NuTrek doesn't give the women any visible rank insignia at all. That's a disaster during red alert. Highly visible is better. Whether you want to advertise rank on a field jacket is debatable. I'd say no. If you don't know whose on your landing party, you're already in trouble.
Well, rank is an important aspect of a uniform, so I too was annoyed by the lack of ranking on the short sleeved uniforms for females. I mean, it isn't like the rankings couldn't go on the cap sleeves, especially given Kirk's green wrap.
In any case, sometimes it seems like rank symbols are treated like an afterthought or a fashion accessory, rather than a requirement on a uniform.
Despite my misgivings about the TMP uniforms, epaulets are a good idea and have worked well for many, many years and worked well on those uniforms. I just didn't like the color scheme.
As for an in-universe reason for the TWOK uniform change, I would imagine that it would be to provide the best amount of coverage, and flexibility given the possibility of changing alien landscapes. Obviously, there are field jackets and uniforms, but in a pinch, the officer's jackets offer a degree of protection, especially given the potential of more futuristic materials, as mentioned before

Also, the uniforms are more, well, uniform. There is a distinct, unifying theme, representing the entirety of the fleet. Given the adoption of the Enterprise arrowhead, the uniform change also indicates a greater solidarity of the entire Fleet, given the crisis with the Klingons.