Running legacy clients (12.1.X) on SEPM 14

I am about to upgrade my SEPM from 12.1.5 to 14.  There are at least 30 clients still running XP (yeah, I know!) Is it correct that they will not be able to upgrade to Client version 14, but they'lll still be ok to run on 12.1.X under a version 14 SEPM?

Also, If I setup AutoUpgrade on SEPM what happens with the XP systems? Will they attempt to upgrade and run into an error, or does it automatically detect not to upgrade those systems?