I don't know if all that is necessary. I have Afterburner set up on my 2x GTX 970 system. It doesn't "start" at boot time, but what I mean by that is that the program interface doesn't load with the initial boot to desktop. Setting the "apply your OC and Fan settings" at startup apparently creates a file that loads at boot time. It doesn't require starting up Afterburner in the system tray at boot time.
As long as I'm passing this on, I have my own dilemma.
I know these programs are more or less agnostic, and I know that Afterburner is popular. Not only is it popular, but it's simply the best such program I've seen among maybe three.
I bought a GTX 1070 Gigabyte (mini-OC) for my Skylake rig. Then, I installed AFterburner without much thought about it. At this point, I'm not ready to overclock the card, but only wanted the program for monitoring.
Then, I installed Gigabyte Xtreme Gaming Engine, more or less equivalent. It comes with three ready-made profiles: "OC," "Gaming" and "Eco." These are all linear speed schedules following voltage on the X-axis, and of different slopes. There is also of course a "manual" feature, which you'd really want to use to seriously overclock the card.
Eco mode shows the clock reduced by 24 Mhz, which appears as a -24 value on the speed slider. So I was asking myself what this means if Afterburner only has values beginning with 0. I'd rather use Afterburner, so I'll have to run some tests to see how speed and voltage scale under both programs. If you say "you don't have to do that," it's just extra trouble to satisfy myself.
But I'm convinced you should only use one or the other -- and not both. The Gigabyte software has some useful "pre-set profile" features, but AB wins hands down for its robust design. But with the Gigabyte software (and I could even be mistaken), it seems you have to keep the program in system tray all the time. There's no "Apply settings at Startup" feature that I've discovered. When I'm ready to push the card to custom settings, I'll want to use Afterburner if I can, and uninstall the Gigabyte program. I would not leave both programs installed together. Probably -- asking for trouble.