Catalina and Mojave

It has been a long few weeks as I am still tackling Catalina, especially 32-bit woos.

I am very aware of incompatibility issues and DID contact the developer(s) regarding the issues.

For example Roxio Titanium -- there is newer version for 10.15 MacOS that I have to spend some upgrade fee.

I am also very excited with Sidecar (after upgrade to 10.15) that I can make music writing/notation without using mouse to mark notes on the score. This function is a huge "yes" for Catalina.

There is always a "however" following -- my family members have been involving in learning few languages and faithful followers of RosettaStones. I got sad news that all my RosettaSones' 5 languages (250 x 5 = 1,250 USD minimum) are no longer supported in Catalina. I did have a conversation last year (when I upgraded to 10.14) and was promised they would make 64-bit version. When I contacted RosettaStones again in October 2019 this year, I was instructed:

a. either buying subscription version (USD 99 for 2-years --> 99 x 5 = 495)

b. or installing these languages in 10.14 or older....

I think I am too cheap to fork out almost 500 USD to satisfy my family. Therefore, I did a dual boot solution, with daring dual internal SSDs (256 PCI-e SSD for 10.14, and 1T SATA SSD for 10.15).

The headache of my desktop will be acted like "community" computer when anyone wants to get to their language programs. (yes, every Mac in the household got upgraded to 10.15, except 2009 Mac Mini Server).

I found I can switch the OS by using "StartUp Disk" -- however, the Time Machine seems to back up both drives (in both MacOS environments). I did use "exclude" selection in TM to make each OS as independent as possible

My question is -- since TM backed up both drives -- will this affect the future "restore"? For example, if we bought a new iMac (such as 2019) and would only want to transfer 1T SATA drive... Will TimeMachine be able to differentiate which drive to be restored?

Thanks

Sam (2015 iMac 27", 24GB, 1T SATA SSD for Catalina, 256GB PCI-e SSD for Mojave)