Except for the CZ-75B (in DA/SA or SA), none of the guns you're looking at are legal in IDPA. They are legal in some IPSC classes, but not all. Probably not legal at all in other forms of competition.
And if you've not competed much (or at all), you need to start out much less grandly. The best analogy: you've never raced a sports car and want to run in a big race, so buy a ferrari. Guys driving hot VWs will be lapping you for a long time to come, until you develop the right skills,
Even after youlve gotten good at the basic, improved your skills, and bought better equipment, some guys will continue to outshoot you, running inferior equipment. Some of the folks we compete against are just flat-out gifted athletes, with superb reflexes, good discipline, and are masters at not wasting a second or a movement. (They put time-motion study experts to shame.)
In racing, having a hot car isn't enough. So it is with competitive shooting.
Start with a good CZ-75B, maybe a DA/SA that has had the SA trigger tuned (you don't need to convert it to SA only, as it will work as a SA only gun.) Maybe a comparable Witness, or the next step up for both lines.
Note: a SA-only gun limits the division/classes you can compete in. Nothing wrong with that, but understand all of the rules and requirements before you dive in, headfirst. The water may be more shallow than you think. Or there may be big rocks under the suface.
Get the proper holster and mag holders, glasses, and ear protection, and just shoot a lot in as many competitive matches as you can. A year from now, take stock and look at moving up in equipment. Others will let you try their guns, from time to time, and you'll learn what works best for you from experience, not buying/trying.
You may want to consider reloading, too, if you don't already do that -- as all of this gets expensive, and some loads may shoot better in your guns than others, and you can't always find what you want in the gun shops.
You're talking about a lot of time, a lot of money, and a big investment, both in time and ego. Do it right and it'll be a lot of fun.