Re: .223 Varmint Upper Build advice...
If this is a walking varminter then I would go with a 18" bull barrel.
If this is a bench varmint rifle. As in you take it out of the car/ truck to a bench then shoot varmints from there. I would go with 24"
I like the wylde chamber because you can get good accuracy out of both 223 and 556 ammo. Plus if you go wylde then you can use it for 556 ammo is SHTF.