One main theme is the clash of personalities. Doofus rick is, well, a doofus, while evil morty is calculating. Their interactions often highlight this contrast. For example, in many fanfics, doofus rick will do something silly that throws off evil morty's carefully laid plans.
I'm not sure if it's still available, but 'Doofus Rick's Influence on Evil Morty' was quite a good one. It examined how doofus rick, with his unique way of thinking, gradually changes evil morty's perception of the world around them. It had some really deep character development and a great plot that kept you hooked from start to finish.
Rick and Morty didn't start as a comic. It first gained popularity as an animated series. The show's unique storyline and characters made it a hit before any comic adaptations were made.
I'm not aware of any Rick and Morty comic in the newspaper. Maybe it's possible in some very specific or niche newspapers, but it's not a common occurrence.
Rick did die in the comic. The circumstances surrounding his death were complex and had a major impact on the story's direction and the other characters.