No need to overthink this. When your Suite subscription expires, you'll get a few warnings and emails that you're going to lose access to the full features of each program, but you'll likely still be able to use them for a couple of weeks at least. See this FAQ for more info.

There is no need to uninstall the non-PD items until and unless you install the older versions. However, you will need to uninstall the Suite versions first before installing the older versions.

Also, the PD19 version of PD365 will magically become the PD20 version next month, and it's the exact same program whether you have the Suite or just the PD subscription so you can keep using it as usual. As long as you have an active subscription, the App Manager will handle the switch and the PD19/20 update without you needing to do anything other than click Install when it's ready.