I have two cranky villagers, if you have three cranky villagers you can still have one of every personality type if you want that.
I think it just depends on your preference. I like cranky villagers, so I don't think three is too much.
I personally think 3 is too many, but I've seen people who have 4 of a certain personality. I wish we could get rid of some villager plots so that we could have the choice of having only 8 villagers - one for every personality type. If you're gonna boot a cranky, make sure it isn't Octavian as he's the best cranky around.
It depends. It might get tiring after a while, but you might love it. In this game, I find that I dislike having more than one normal villager at a time because they feel too similar in this one. While in New Leaf, that was my most common personality.
I mean, I have three normals on my island, and I'm not tired of them yet. As others have stated, it comes down to your preference. For me, I can tolerate having three of the same personalities because I'm fond of them. But if you're not the biggest fan of them, perhaps you may eventually regret it. If you're not concerned about getting all the personality types, just go for it.
It depends on u and what u like. I've got 3 normals and will probably get another. Some ppl would find the dialogue repetitive for multiple villagers of the same personality but idc.