I havent seen any rigorous tests of any of those here, I doubt there is a consensus.
Some thoughts tho:
1- The desired avoidance of precipitating zinc is from published chemical literature. Professional chemists like to avoid anything that might slow them down, be inconvenient, or marginally reduce yield. We tend to have different priorities, and often less access to the chems and equipment the researchers have.
2- I think there is a consensus here, or a tentative one. THH doesnt precip in a manske salt precipitation. If used at all a manske would then just serve to remove residual harmine and harmaline from the solution.
3- You wrote it backwards

run the reduction in ammonium chloride solution, and then precip the THH with ammonia. Obviously, if no ammonium chloride is on hand one could a) add hydrochloric acid to ammonia b) add the alkaloids and zinc c) after reaction add more ammonia.