Zim: There are a few flaws in your theory. First, Nero's wife had hair, and so did one of the female crew members, so obviously Nero and (male) crews' baldness is of choice, not genetics.
And I can think of many reasons why his crew shaved their heads. Perhaps it's a culture thing with the mining guild he belongs to (tattoos and all). Maybe they didn't want excess hair getting caught in machinery, as there's all sorts of moving parts in the Narada. Maybe the ship gets really hot inside, and they just want to cool off. Maybe it just makes them feel like they're a bunch of badasses. Etc.
Second, there are aliens (such as Klingons and Bolians) even in the TNG era that look extremely different from one another, and yet are the same species. So why not the Romulans? Plus, it could be a culture thing too. Maybe the brow-ridged Romulans get to be warbird crewmembers, and the non-brow-ridged Romulans work as miners, just like the poor Nosferatu-looking Romulans have to mine dilithium on Remus.
Third, a mining vessel is going to look completely different from a warbird, based on its function. Just because the Narada is big and tentacle-ly and not shaped like a bird means nada. Does a bulldozer look like a police car?
Honestly, these are very flimsy points to base your hypothesis on.