I used to shoot in IDPA matches every weekend until my knees gave out, that was at least 10 years ago.
At that time the Glock 34 was the go to gun.
The rules have changed since then and new categories have been made. I used to shoot SSP and first used my DA/SA Sig P220ST. I later moved to the CZ Shadow. Back then it was iron sights only.

What gun are the top shooters ( those that are not sponsored) use today?

Glock is still number one, CZ is probably number two. I know Walther has been making big inroads in the past couple of years and is my current go-to.

Ran my first IDPA match a week ago. I was surprised to see so many different pistols. CZs, Caniks, Glocks, Sigs, S&W M&Ps all scattered throughout. I would guess P320 variants were the most common and was surprised to see so little Glocks that day.

There are plenty of Glocks around here, but the other striker fired guns are catching up in SSP.

Carry Optics is the growth division, the most entries at the clubs I shoot at, over 1/3.

And USPSA is overrun by CO, with the provisional Limited Optic doing well. My last USPSA had only 3 iron sight shooters, me included.

At my local club a lot of people put away their Glocks and bought P320s. Almost everyone (85% or more) shoots optic now.