More times than not, seed sellers are a dime a dozen. Not much differentiates the average seed seller.
If they aren't selecting plants for breeding from large samples and taking years to develop a strain, it's just a pollen chucker. Sometimes they are just bulk resellers, sometimes they buy some 'real' genetics then breed it with some inhouse plants and call it a day.
unfortunately, word of mouth is often the only thing we have to go by. That's unreliable more times than not too.
Even with 'bulk' sellers you can fine awesome plants. Start breeding your own. If you start with high quality, you get high quaity. You can do what 80-90% of these so-called breeders do, lol. They use methods from the 1800s and they don't even follow those methods well. (mendellian genetics)
My one suggestion - Don't over-pay for seeds. You'll just be buying a name.