Never a problem mixing “RED BRASS” with copper except the coefficient of expansion will be different do to the mass of the brass pipe compared to the much thinner wall of copper tubing.
Red Brass is made up of 85% copper 15% Zinc BUT Yellow brass is 60% copper 40% Zinc and you could get dezincification (Brittle piping failures)
What happens when mixing copper/Galvainzed pipe if galvanic action and thus
Actually if your looking for strenth your better off with brass piping and T.P copper Brazed joints and not threaded as all threaded brass schedule 40 is only rated to 125 PSI WOG DEPENDING on temperature.
Send me a private E Mail and We can discuss applications as we dont want to give the ditch digger or the helper a head ache trying to understand REAL PLUMBING principles.
At least your smarter then asking a home center stock Clerk LOL