Are these the same for all companions or do they differ? Is there a way to figure out specifics like carry weight limit/HP/SPECIAL/etc.?

Special stats and carry weights are listed on the Fallout Wiki. (Not sure how accurate those are. Some of the carry weights seem lower than I'd expect...)

Those seem wildly inaccurate. Preston has an intelligence of 8 and Curie's is only 4? Um, what?

That or they aren't meant to be reflective of the character's non combat abilities.

In Preston's case I would have estimated it to be 1.

There's this: https://www.reddit.com/r/Fallout/comments/3vm4ng/fallout_4_companion_information/ and it seems to support INT 4 Curie.

Strong's luck is 1. Lol. This makes me not want to stand too close in case of anvils or pianos.

Yeah, like I said, not sure about the accuracy of those. We probably won't know for sure until the GECK is released though.

Some also don't have them listed, like x6-88.

My player luck is 1. And I'm doing fine so far.

Mine is as well. It doesn't seem to cause any consequences. It's just given how comically high all the other companions SPECIAL scores seem to be, it just made Strong seem like the Wile E. Coyote of the lot.