Welcome Shep to the PB forum. Glad you joined us.

The most important thing is to find a very good and trustworthy hatchery with people who know what they are doing and will answer questions. If you can find 2 or 3 even better. IMO price should not be the major factor. Knowing what you are getting and about the brood stock from which they came and that they come from a similar climate is much more important IMO.

The mixing of genetics question is a much harder. Here is why. When you buy from hatchery X the fish may be from 10 pair of brood stock or just 1. If X's are from 10 unrelated pair and of good genetics that may be better than buying from Y and Z who's fish are from 1 pair each , at least for diversity of genetics reasons. Here is another point. You never know for sure about genetics -- are X's fish better than Y or Z's , unless you can tie other purchasers fish back to the brood stock and compare them from the same pond and time period. Very hard to get and apples to apples comparison.

I personally like to mix up the genetics after careful study of what I am doing as set out above. That does not mean you always get better results.

First things first. Most of the success of growing good fish is water quality and forage/fertility with a smaller part being fish genetics. Unless you have the first the second does not make a lot of difference. When you have the first then the second can make a significant difference.