Why?
MyDMX is its own "world" unto itself.
Quirks with fixtures can vary from user to user and fixture to fixture.
Hardware it is running on? That's why there are specs for minimum recommendations and suggested configurations.
Cabling: if you don't understand basic DMX cabling, then you need to take a remedial course in lighting and DMX.
Power Distribution:
That's not a MyDMX issue, and unless you're listing your rig, it's hard to give advice.
You're asking for stuff that has nothing to do with MyDMX.
Here's some best practice: have your system totally trouble-shot and confirmed working properly in the current software load(especially after updates to MyDMX and/or fixes, updates, hot fixes, and other software chages to the OS and hardware) before a show. And in my case, my best practice includes a fail-over solution of having a hardware controller readily accessible. I also recommend configuring your fixtures to align with a conroller for fail-over reasons. This may mean some wasted channes, but that's a small price to pay for a logical layout. MyDMX lets one really utilize all DMX channels easily. Since I insist on compatibility with my DMX operator, sometimes there are "holes" in the channels, and that's just how it is gong to be.
It's really best to keep these sort of topics sepparate as they are not all lumped together as you may feel they should be. I understand your point of view.
MyDMX failed on me at a show, and I had my controller handy so I patched right to it and kept on going. Why? Don't know, don't care why. Mad? No. Annoyed? Sure. But next show, I'm using MyDMX again and if it fails again, I'll again fail over to my controller. This will be standard practice. But, I somehow doubt MyDMX is going to fail on me again. I am committed to using MyDMX, and I will have success with it.