I normally work with several versions of GeneXus installed on my computer, even with several upgrades of the same version.
The installation is done directly from the .zip and then GeneXus /install.
The query comes because, as part of the process, I add the following keys to the genexus.exe.config file:
<add key="UserAppDataPath" value="C:\temp\Genexus\GX17UBeta\UserAppData"/>
<add key="ProgramDataPath" value="C:\temp\Genexus\GX17UBeta\ProgramDataPath"/>
Currently I do it out of habit and I am not sure if it is still necessary.
You don't need to do that setup.
Everything should work OK without making those changes. It can be useful to make sure that the configs and temporary of each version are completely isolated from those of another upgrade you have.
What yes, if you do NOT use those entries, before opening a GX you have to execute a "/install" first so that the cache of packages that has that version of GX that you are going to use is updated, especially if you have patterns installed in GX.