How many problems can I expect?
Depends a lot on the details. The main problem with self connections is missing the connection. If you do miss it, you are fully responsible. The connecting airline will treat you as a "no show". In the worst case, they will cancel your ticket including any return flights and you may have to buy a new same day ticket on the spot, which can be VERY expensive.
What if buy "meet and greet" service, where might they wait on me and will they help with getting my baggage, rechecking if necessary .etc?
In my opinion that doesn't help much and it may cost more than the price difference to a normal ticket. They are often not allowed in the secure area and they can't make your bags come out any faster.
Do I need a visa on arrival
Yes. You will have to go through immigration and customs, enter Kuwait properly and then go to the check in counter of the second airline.
What else might go wrong or be a hassle?
It's a significant hassle as compared to a normal connection. You have to line up at immigration, then wait for your bags, you may have to line up at customs. Your second airline may be in a completely different terminal, so you need to figure out how to get there. Then you need to line up again at check-in counter of the second airline. You need to be at the front of the line BEFORE the check-in deadline. And when you finally have your boarding passes and dropped your bags, you will line up again at security.
I only recommend self connections for experienced traveler who can look at airport layouts and track records for immigration and delay performance, who can assess what a reasonably "safe" connection time is and who have some idea about "Plan B" if things go sideways.
A lot depends on your specific details (which airlines, which flights, terminal layout, etc) but I would not do this under 4 hours even if the details look good.
Note that some companies like KIWI offer a "guarantee". I recommend reading the rules, terms and conditions VERY carefully and Google some customer reviews.