First, confirm that typical rifle rounds are allowed. In my local three gun, only pistol caliber carbines with non-magnum, non +P ammo are allowed.
Second: I like the CA model. I like the more rugged front sight design (on the gas block, not the cheap barrel mount). I don't mind that it won't fire when folded. To me, the folded position is just for storage. Speaking of storage, I like that it still has the storage stock for mags.
The only real thing wrong with it is that the price is now into Mini-14 territory, due to lack of supply. The new Mini-14s are better rifles, IMO.
For sights, try the stock aperture sights first. A small 4X may be in order.
If you're limited to pistol caliber carbines, consider the Sub2000 instead.
I went with a Marlin 1894 for my three gun rifle. I love the feel of it, but haven't shot it yet, due to a manufacturing defect. (buy a used older model, if you're smart, as quality has gone down recently)
"Well begun is half done."
-Aristotle