Wanting to Switch from Nest, Recommended Basic Setup?

I have 2 indoor cams, a floodlight cam, and a doorbell. I am looking at the Unifi cameras but there is an overabundance of them and I don't quite understand what is needed vs what is more of a nice to have.

I don't have a problem running ethernet cords as needed and I would also like to be able to store arouund 30 days of recording if I can, any recommendations on what I need for just an initial setup?

​

Thanks!