Megaparrots spawn very often and in almost every biome. It takes away from the fun of discovering them, and fills the animal mob cap with them (parrots can't produce wool or milk or leather y'know lol).

It should be up to the user/server admin/modpack maker to choose how often they'd spawn and where.

Currently, they only spawn in 6/18 biomes, so I am not entirely sure what you mean. Additionally, they also only spawn with a weight of 15, this is slightly higher than Sheep (12), Pig (10), Chicken (10), and Cow (8). I have had a lot of requests for a config so I might get around to it but it's a low priority for me as I am just one person with limited time.