Stages have specified load outs, and the majority of time you have limited engagement on each target. Tactical games is very accuracy oriented, there aren't many hose it down stages and most of the time the distances are limited but smaller than usual targets are used. You need to know your holdovers and height over bore but won't necessarily need DOPE at extended ranges.
Dont expect to be changing mags much in the middle of a stage either, they really limit mag changes and hot holstering, likely due to the fact that people are smoked from the fitness while shooting so they are understandably reducing their liability. But every now and then they will get outside the norm on a stage.
The fitness part is tough, I would say especially for smaller guys like myself where the weight can become a problem, but there are some smaller/guys and gals that crush it, blowing that argument out of the water. With that being said I was able to, surprisingly, complete all the fitness stages, though some of them just barely inside the par time. FWIW I have more of a skinny runner/surfer frame than a CrossFit frame. Most who do very well in the fitness, uh... don't look like me.
The shooting is "easier" than other shooting sports IMO, so if you compete in other shooting disciplines regularly, you will shoot toward the top of the field fairly easily. The hard part is "easy" shooting becomes difficult shooting when you are gasping for air and trying to maintain an unsupported sight picture.
I would work on strength, endurance and V02 max. You can compete pretty well as a good shooter and any one of those 3, but if you are trying to win, you will need them all.