[arghwhat]

Wow, what a mixup of terminology.

We're on a thread about residential internet modems. In this context, "coax" means "DOCSIS" (i.e. internet over cable TV), as opposed to fiber and telephone (DSL). UTP is absolutely useless as a residential uplink, as 100 meter gets you nowhere. Telephone cables are shit, so DOCSIS and fiber is where its at.

However, you seem to be talking about direct attach cable ("DAC"), which absolutely no one mentioned. As someone who worked at a network equipment manufacturer, absolutely no one calls direct attach cables "coax". They're often called "twinax" (which is a type of coax), although this terminology is misleading and entirely irrelevant. Also, they're kind of pointless these days.

And no, while 10GBase-T is a thing, the pluggables are too expensive to make the activity worthwhile. Run fiber—it's not really more expensive, and it's future proof for when you need to setup 25G or 40G soon.