these are my current settings and understanding:

use of memory: you want programs first. meaning whatever you have currently open gets optimum use with the system (cache) being second. This doesnt matter if you use othe machine or leave it idle or DC'ing (the memory is always best allocated to the open program).

best performance: depends how you setup your DC programs. If they are setup as services (e.g as DHEP usually is) then background services would be best. but if you double click a shortcut or .exe then program is best. Whilst you are using the machine program would be best as running outlook, word or whatever else is a program not a service.
Whichever you set priority to, the remains still go to the other, so programs then services or services then programs. If you leave it idle and dc'ing 100% should still go to either it may be slightly slower going through programs first but anytime you use the machine you would want programs as 1).