I've been thinking of what you could do for this but there are so many different edge cases that it seems like it would be impossible with just Quick Base. What if a user entered their middle initial? Or had a name like RonaldMcDonald, where the last name has 2 capitals.

You might be able to make a monster formula to do this but it would be ridiculously huge I think. I would explore using an Excel formula to do this, just be mindful of the edge cases like I mentioned above. You could also take the excel formula and attempt to make it into a Quick Base formula.

https://www.extendoffice.com/documents/excel/3336-excel-split-text-by-capital-letter.html-

If you do it this way you will need to fix whatever is causing you to get the bad names like that. You really really should have a delimiter character in there to help with issues like this. I have always used separate first and last name fields because you can then just make a formula field to concatenate them together if you need that and it will be formatted the exact way you need.