I've found almost nothing about the company (quite the generic name, right?) other than the phone number listed seems to be in the UK and there's a Trustpilot score.

I was looking for info on Empire Total War and Egaming came up, but doesn't come up on any price search sites I use and never heard of anyone purchasing there.

Their "About Us" page claims that Of course anyone can say anything on the Internet, regardless of whether it's true or not. Their prices don't appear suspiciously low, they are comparable to other storefronts, while shady sites (either key resellers or scammers) tend to try to draw people in with ultra cheap, too-good-to-be-true deals. All this is just to say it doesn't appear at a glance that they are a grey market reseller. Whether you can actually trust them or not is another matter entirely.

As detailed here:
https://www.gog.com/forum/general/has_anyone_used_the_website_bestoldgamesorg
If the store is not GOG, then the store is a pirate website and it is your responsibility to follow up with publishers, and if necessary spend your time and money taking them to court.

It might actually be worth contacting GOG directly, since the site in question is selling Cyberpunk 2077 keys that apparently redeem on GOG. There shouldn't be any other source for those keys than CD Projekt Red themselves, which means if they aren't legitimate you can assume the rest of the site isn't either.

bit of an alarm bell.
that said, Greenman Gaming had Witcher 3 GOG codes some years back. While GMG are otherwise legit, theyd purchased them through some Eastern European distributor (who did get the keys from GOG / CDPR). Not a "straight" deal - definately fishy, but not entirely illegitimate either.
pretty sure GOG / CDPR would have tightened their contracts since though.

How GOG could tell? They can sell legit keys from boxes or gift codes from GOG. Lots of resellers sell GOG games.

by buying one as a test.

But still what could possibly come out? I never heard of counterfeit GOG keys. Worst case scenario they're selling gifts bought in Russian or other cheap region, that might be not ok but hardly illegal.
If keys are bought with stolen cards there is no way to verify.

that really depends on where you live and where you trade from.

its a breach of GOGs terms of service at the least and makes the store a grey market scum site - contradicting their "Our products are competitively priced and sourced directly from the publishers and authorized distributors." statement - making them even more dodgy if thats the case.