Any version of Vegas Pro can exist quite happily on the same computer without a problem. Some on the forum have installed on the same computer versions of Vegas Pro going back over 10 years.
without creating two separate folders worth of content?
I have limited computer space, so I'd rather not have to separate versions of Vegas with their own files and folders. That's what I meant by 'content'.
Different versions of Vegas Pro are separate programs and therefore do have separate installs on the C drive - so yes, have their own files and folders on the C drive constituting - as a guess - around 700-800 MB each.
I read somewhere on these forums that if you get a Humble Bundle with a newer version of Vegas, you can get the upgrade from MAGIX.
Please understand that the VEGAS Pro 16 serial number you get with the HBundle purchase makes it eligible for upgrade pricing if/when you want to purchase the latest version of the software.