Separate folder for projects on going to PrPro 2017? Still keep 2015?

I just installed PrPro 2017 and deleted PrPro 2015.

Other than adding _1 to the filename, it seems when you open a project created in 2015 with 2017 nothing much changes. It doesn't ask me to do Save As to give it a new name, or to put it in a new folder, and it doesn't give it a new extension. It just puts it in the same folder as the previous version of the project.

Is this probably good enough for a basic business user doing our own in-house business videos? Or is it a lot better to create a separate folder structure for projects created in (or converted to) 2017?

(Interestingly, I don't see any way to determine if a project was saved/created with 2015 or 2017, such as by looking at Properties > Details.)

For that matter, how many users who went from 2015 to 2017 found it necessary to still have 2015 installed? Or is it "usually" fine to open those projects in 2017 as needed (which I presume "converts" them to 2017 projects) and never look back?

Out of prudence, as soon as I installed 2017 I cleared all my media cache folders -- manually, while PrPro was not running. Should i do the same for all Preview folders (which I presume is the same as saying "where my Scratch Disk path is directed to" -- which I keep in one common folder structure, not with each project)?

Anything else I should know about the upgrade process at this time?

Thanks!