Late to the party here, but did you ever figure out what was causing your delay when doing a scene? Im in the same boat you are/were except I am using Home Assistant. See thread: Frustration level 100! Scene commanding 5 red dimmers can take over 20+ seconds to complete - #13 by nappyjim
I’ve tried to rule out everything. The only things I havent ruled out yet are the dimmers themselves, as they are currently the only Z wave light switches I have. But as of Saturday, I will have a couple {gasp} non-inovelli switches that I will be testing the scene on (sorry Inovelli, but I have to rule out the switches) ((I really really REALLY hope its not the switches themselves as I have spent over 1k on 30 switches in the past 2 months))