The rule pelaird quoted is the one that applies to you, since a subscription started now is a new one rather than Classic. On lapse the suite software stops activating, and there is no carve-out for the apps that are also sold on their own.
An Object Desktop year does not hand you a perpetual licence for DeskScapes or SpaceMonger. Those are separate purchases with their own serials, and one you have bought outright is not touched by a subscription running out.
So it is either/or rather than a cheaper route to the same thing. Buy the two and you still have them in a year. Subscribe and you have the whole suite for the year and nothing running after it.
If those two are the only ones you want, buying them is the simpler answer. The subscription is worth it if you expect to use several of the others, and renewing keeps you on the current versions of everything in the suite.