What is best for an URL: upper case or only lower case

Question

At this time we have URLs formed with upper cases like this:

mywebsite.com/us/Fine-Art/

And we want to add artist names like Van Gogh, so is the best for SEO to continue with a mixed of upper case and lower cases, like this:

mywebsite.com/us/Fine-Art/Van-Gogh

Or only lower cases for the artist name

mywebsite.com/us/Fine-Art/van-gogh

Or maybe remove all upper cases, even to what is already indexed by search engines, we will perform 301 redirections to new urls :

mywebsite.com/us/fine-art/van-gogh

Answer 1

Go with lower case always, avoid uppercases, underscores, parameters etc.