Munchkin codes

Sure.

The only edge case to consider is that GTM, by its very nature, adds another level of async loading. That is, the GTM JS library itself loads async, then it injects your matching tags async. So if the person navigates very quickly away, Munchkin may not have had a chance to bootstrap and send its initial hit. Exceedingly unlikely... but technically more likely than if you had the Munchkin embed right in the original document. (This is the case with all tag managers.)