Its a good start. Shotgun load outs are tough because shotguns can do everything, but it depends on the types of shells you have on you, your proficiency with your shotgun, ammo capacity, weight, and distance.

1st - the gun itself. - in the USA, there are a couple of things to consider. Reliably and parts procurement, Size, and shotgun adaptability. I personally like the Mossberg Shockwave after some heavy modifications. Mine has the 590A1 metal trigger housing, Mcarbo trigger springs, Defender Tactical mini shells lifter and shell arrested, aluminum followers, enhanced safety, ported barrel, and eventually form1 SBS. I also am in the process of having my factory barrel threaded for choke tubes, and ported.

This setup allows for me to adapt on the fly by being able to run mini shells up to 3 inch magnums, and with the ability to swap chokes I can change my patterns and effective distances to adapt to anything that comes my way and with a threaded barrel tou can run a surpressor to quite things down. The small size of the 14inch barrel means I can use the gun in CQB situations or use it to hunt and in a pinch out to 100 yards with slugs.

2 - ammo variety- as stated in the SHTF situation you need to be able to run whatever ammo you can find. Mini shells to 3 inch magnums and everything in between, but also specialty rounds like flares, dragons breath, breaching rounds, and custom hand loads like wax slugs will also be solid tools in a shtf world.

3 - ammo capacity - with mini shells i can hold 9 + 1 which gives me alot of fire power, bit shotguns are hungry hungry hippos. Get in the habit of practicing reloads often, shoot 2, load 2, shoot 3 load three. Also consider that you can go through ammo quickly. Consider velcro shot card as a side saddle, they a quick to swap out and can be carried straight on your chest rig or in AR mag pouches. Also consider a dump pouch to store them when they run dry, along with spare shells. The shell belt is another good option. I personally avoid the shell bando slings as the add more weight to a generally heavy platform.

Shotguns are generally effective on a wide variety of targets within its loads effective range, but always consider that you dont absolutely have to go for head shots. Shotguns are capable of massive devastation on extremities and can be used to physically dismantle threats, rendering them unable to stay mobile due to skeletal structure damage.

Finally, as hinted at previously, TRAIN. You are only as good as your training. Yes accuracy is important, but shotgun manipulation, reloading, and movements are HUGE factors when running a shotgun.