You bought one of the many rebranded shotguns coming out of Turkey, all of which are of questionable quality. I would not expect it to last more than 1000 rounds without a serious part breakage and it may or may not work well at all until then.

The chokes are for forcing the projectiles of a shotgun shell into a tighter spread. Cylinder is completely open, then Improved Cylinder, Modified, Improved Modified, and Full are each more restrictive than the last. I don’t know which chokes your gun came with. For home defense distances I wouldn’t worry about it too much, you’re not going to get any appreciable spread regardless.

I don’t know why a review says you can’t use slugs, maybe they have a good reason, maybe they’re overreacting or misunderstanding something.

Don’t use dragon’s breath. A fellow in New Jersey recently started a wildfire with one and went to prison. They’re useless for most things anyway.

Flechette rounds aren’t really worth considering. Expensive and their effect on target is dubious, especially considering many makers use low-quality flechettes salvaged from artillery-sized shells.

I was curious about the why’s of it so I googled. I do not own the shotgun or have personal experience with it.

https://gforcearms.com/faqs/

They say you can do it, but use the right choke. I’d say take it to the local gun range and ask them for advice.