You can. It adds a lot of work! It's surprisingly tough to sand. And sanding makes it look bad, so you end up having to use filler primer and/or bondo, then more sanding, and more painting. Here's an example: https://www.youtube.com/watch?v=ZTE9bJyUO_8

You can also do something caled "vapor smoothing".

You can also use "adaptive layer height" in the slicer settings to greatly reduce it.

Yes, you can. If you want to do that, I'd recommend to print in ABS though. It's easier to sand and you can use vapor smoothing afterwards to get a very smooth and shiny surface.

Printing ABS is more challenging though and the fumes tend to smell.