Answering three topics: IWB, belt, spare mags.
I carry IWB at 4 o’clock on a $60 leather belt from AGN Leather at NCC Farmers Market. The spare mag is in a mag pocket of 5.11 TacLite pants. Been wearing this belt for 15 months with no sign of wear or sag as opposed to a $20 Tractor Supply belt that developed a weak point after a year and never provided the same rigidity. I prefer IWB for profile and interference, i.e., closer to the body with less banging on door frames.