From the pictures this a stainless steel barrel 1:8 twist. By looking at the Key Mod hand guard and barrel markings I’d say it is probably a Bear Creek Arsenal barrel and hand guard. Might be a home built or purchased as a complete upper. Either way I’d shoot it with some factory ammo first and see how it functions.
If you decide to switch to an adjustable gas block you need to figure out how you’ll reach the adjustment screw. If you get an adjustable gas block with the screw on the front your going to have to remove the hand guard or get a an extension for the allen wrench. You might get lucky on a front adjusting GB to reach it through a key mod hole on the side with an angled allen wrench. If you get an adjustable gas block that adjust from the side you might get clearence. You can always drill a small hole or modify the hand guard to get to the adjustment screw if it’s on the side.
If you decide to switch to an adjustable gas block you need to figure out how you’ll reach the adjustment screw. If you get an adjustable gas block with the screw on the front your going to have to remove the hand guard or get a an extension for the allen wrench. You might get lucky on a front adjusting GB to reach it through a key mod hole on the side with an angled allen wrench. If you get an adjustable gas block that adjust from the side you might get clearence. You can always drill a small hole or modify the hand guard to get to the adjustment screw if it’s on the side.