Newbie - Which is better tiny bunkhouse or hybrid

I agree with seriously checking the vehicle's payload rating. Subtract the weights of all 5 people and see what is left for camping equipment that won't fit in the trailer, and trailer tongue weight. Report back what that number is and we can give you better answers.

Also, look at the label attached to the trailer hitch. What is the max tongue weight it lists?

Forget it you're not going to tow a trailer big enough for 5 with a crossover. I've got a half ton truck with almost 1,700 pounds of cargo capacity and I'm nearly maxed out with 5 of us in the truck hauling a 3,000 dry/3,600 GVWR trailer. An SUV with 5 people in it is going to be massively overloaded with a similar setup. Your best bet is to find a popup with the lowest tongue weight you can (many of the bigger high sided popups are actually heavier on the tongue than some light hard sided trailers) or upgrade to a crew cab pickup (from experience I'd say a 3/4 ton or at the very least an F150 with the HD payload option). The only other option I could see would be two vehicles, one to haul people and gear and the other to tow the trailer.

For the size of trailer you can tow I see at lot more of the hybrid trailers in the campgrounds. I think the extra room is the reason.

Now having owned both (hybrid and TT) here are my thoughts:

Hybrid:
* Lighter for the room (no floor space is lost to beds)
* likely has bigger beds (ours had three queen beds)
* opens up to the outside better (think like a tent)
* beds will have higher weight ratings in most cases compared to bunk beds
* beds will be bigger than bunk beds (finding bunks in a TT that fits my 6 foot plus son with broad shoulders was really hard)

Trailer:
* Warmer in the winter and easier to cool in the summer
* better to keep the noise of the campground out (think getting kids to sleep next to the party by the fire next door)
* no need to fold up beds when leaving (less work to leave and set up)

Things that are mostly the same (not exactly, but similar)
* risk of leaks --- really the same on both. We had our Hybrid for 10 years, zero leaks... many TT don't go that long before leaking
* cost of maintenance
* towing - assuming you have the right set up on both

Given your vehicle, I would suggest the Hybrid if you find one in good shape (used) or new. You'll get a bit more livable space.

The GWVR is 5000 dry weight must be 3500. So either should be fine.

Your Kia properly equipped has a max tongue weight of 350Lbs. That 3500 dry weight will quickly become 4500Lbs. That will leave you will over the rating of your hitch. don't know the cargo capacity of your Kia but if you add passangers and cargo and tongue weight I assume you will be over weight there also.