My suggestion for "on the fly" control is as follows:
I intend to mainly make scenes that are color washes. I have a great many lights for that. I have 32 Par 38's, which I have gel'ed Red, Green, Blue and Yellow, so 8 of each. 8 Par38's /T-bar(4 up, 4 down). Color Fusions. 64B LED Pros. I have some color changers and movers.
So, using well named and organized banks of colors suits 99% of my needs. I can combine any type of lights. "Oh crap, I want pink...." hit the LED 64 PINK button. While not perfect, for me it is ideal
I can put my colors in 64Bs, then in Color Fusions, and as my other color changers and Par38 banks. Then, banks of scenes that combine, such as "all Red, all Green..." and others like "64B and Color Fusions Red, Pink..." Just organizing to keep things easy to find. Click, click, click. Maybe not ideal, but syncing to music isn't necessary for me. I can just throw a scene up per song and it gets the job done. If I want fancy, I can sweep between a few scenes in a song on a timer sequence. Button triggers for blackout, fade to black/blackout and a soft white between songs.
Why can this be weak? Well, if you want to do some real-time stuff using multiple fixtures(especially not like for like fixtures), it can be clumsy. It's not the software's fault, it's just a limitation of the software. In a live situation, controller surfaces tend to be the better option for "on the fly" stuff, they just have a tactile interface more conducive to that sort of thing.
Now, there are ways of grouping faders in MyDMX. I forget, but I know it's there. But for me, color washes get the job done. If I need a manual feature, I have specials I can on/off via other faders in My DMX and none of those are "critical"
What works best for you is determined by how you work and what you want to do. I think doing "real time manipulation" of a moving head fixture might be a bit more than MyDMX can do for you. Not saying MyDMX bites, but rather, how do you manipulate 2 faders at once for the X and Y axis? Because you can do a vast number of scenes, you might just consider "hey, I'll do a circle in red" and then "circle in red with Gobo 1" and then "Circle in red with Gobo 1 Rotating", stuff like that. That's also what I plan to do. Like for example, with my weddings, I'll do a scen that has the movers pan down to up and then to the back wall in red(lucky color) and use a specific gobo(no bounce or rotation, gobo not determined yet), as well as wash the stage in soft red, specials off. this is for the "entrance of the bride and groom" afer family introductions(please don't ask here, hit my site if you want details as to how these things go)
I say make lots of scenes and name them very well and organize them. Looking at what MyDMX did for my QSpot150's for circles, that was a lot of movement, very specific using 2 faders. It was nice to have the MyDMX software tackle that for me. That alone was worth the price I paid.