As to the supplements that is really going to be determined on the food you chose. When i was feeding Taste Of The Wild, for instance, i would use 100% organic Salmon oil for the skin and coat, mixing in with their kibble during feeds. When i switched them off of Orijen, i have not needed to add anything to their kibble and results have been far superior to any feed i have fed to any dogs both current and past.
Aside from quality of feed and whats in the feed, all dogs will react differently. You may be able to feed Evo, for instance, with zero supplements and fair exceptionally well.. Or it may turn out the high protein may be an issue or you may need to add some oils or other supplements to help with a consistent growth pattern.
Unfortunately theres no real right or wrong answer to give, as each pup will be different.
Some foods i would recommend:
Orijen
Acana
Evo
All are high protein, i have always fed high protein feeds to any dogs under my care and never had any issues that you may hear about again the foods, of course all dogs are different however if fed properly, plenty of water, so on so forth i have never ran into any health problems.
As to the breeder, here are my problems with them.
1. They advertise online, generally speaking online advertised breeders are in it for profit vs benefiting the breed. Not always, of course however it is a red flag. I have never gotten a pup from someone that advertises on the web, flyers, papers, etc.
2. They advertise "Red Nose", generally this is a huge red flag for BYB as the color of the nose has zero to do with anything.. except color of the NOSE. This alone makes me back away.
3. Pricing is high, very high. I have never paid over $300 for a superior pup, its all in who you know. Now, this is going to differ person to person as a pup is only worth what someone is willing to pay. But personally speaking, their prices are high.
4. A few of their dogs i question both peds and sizes.
All in all they don't seem to be anything special, i also don't see anywhere about health testing though they have a "health guarantee" spot on their page it doesn't go into details with that means. They may test but i dont see anything about the actual testing. I'd say they are a typical, "internet" breeder just based on a brief look about.