The one pictured should be threaded. Prob with its own barrel nut included. Tighten barrel nut,thread on the hand guard then clamp it on with those 3 screw holes you can see.
And for that price,primary arms has seekins rails on sale.
I agree. This was my first build and it's not overwhelming at all. The hardest part is figuring out what to buy! Lol.
OP,give Steve a call at @SR Armory,he's right around the corner from hi caliber. And has a few built ar's and plenty of parts in his shop you can check out.
Why not build one exactly how you want?
I'm almost finished with my first build and they are super easy with a few tools.
built the lower laying in bed.
and finished the upper and lower after work. All I need is a barrel and I'll be shooting.