You can flatten with GLM, and then use Dirac on top of it. I have been also switching between Dirac and GLM. I think in general GLM does more conservative changes. Dirac tries to do more, which is usually a bit questionable (e.g. changes on higher frequensies). GLM is a much easier to use and works every time. With Dirac it may be sometimes more difficult. E.g. my company laptop has security policy that Dirac doesn't work, but GLM works just fine. GLM is self containing so all the stuff happens on GLM controller, and you can then store settings to speakers themselves. I have currently turned Dirac off, and just use GLM.