Hello "Sir"!
Welcome to SimplyDiscus!
That question on strains is one we have had here in the past. The general consensus is that it doesnt matter to them and thats been my experience as well. We as hobbyists see all these strains as different by their color.. discus see discus. If a female is ready to lay eggs she will with whatever male she pairs up with.
As for the other question, it doesn't matter if they are grown together put together after adult.. if they are ready to breed and conditions are right..they will breed. That said... often times a way to trigger breeding is to mix things up. If you have a stable quiet tank, alot of times adding fish will trigger spawning.
Are you currently keeping Discus?
Al