What’s the typical loadout for a subgun?

I’ve got a sp5k with the micro rig from Haley on the way.
Holds 4 mags. I’m thinking total of 7 mags, 4 chest 2 belt 1 in the Sp5k.  3 pistol mags? Two on the belt one in the handgun.
Blue force minimal ifak, comms pouch, dump pouch, flashlight in the chest rig, multitool.

Anything else?

Mission drives the equipment, so what are you using it for?

During a portion of my active duty time I had an MP5 issued to me. I carried a pair of mags with an H&K clamp on the MP5 and found that a clamped pair of mags fit nicely in an M4 double mag pouch. Be cause of this I carried 8 on my chest and 2 on the gun.

Now as a LEO, SMGs are dropping out of favor. But for the entry teams that do carry them, you rarely see more then 2-3 spares on the vest. SWAT teams are not anticipating a protracted firefight for 99% of their work.

For a home defense, grab and go, etc.... I really can't see the justification for more or even as much as your carrying now.

The m4 pouch you speak of, is that a Velcro Molle type?
For me I’m looking for grab n go shtf.

Not really a subgun load, per se, but for my 8” PSA 9mm pistol, I use an HSGI AO carrying six Pmag21’s and a small BOK.

It works.

They were just TAG M4 double mag pouches. Nothing special. I didn't want to change my armor's pouches for the times that I traded my M4 for the MP5 (Often against my will...)

Now there are far better options with swift clips and placards, etc.

I run a Glock AR9.  I have found that stick mag will fit two wide in an AR mag pouch on a chest rig.

I have considered some kydex carriers on a custom rig like an HSGI AO I build up on my own.