I use two carry guns, Glock sub-compact and S&W J .38 2 inchers.
Both can be appendix carried but the J is a bit easier if you have to bend over much.
Long barrels do not work well as they stick into, ahem, delicate places.
Make sure the IWB is THIN! A thin holster means less printing.
“We can evade reality, but we cannot evade the consequences of evading reality” Ayn Rand