DIFFERENT RAM dual channel?

Right now i have 4 ram slots

Currently i have 2 sticks in it that are running in dual channel mode. they are the exact same chips

If i buy 2 more ships to but in the other 2 slots but they are different brands and speeds then the ones currently in there can i run those 2 in dual channel while running the other 2 in dual channel?

would they affect each other?

If you add more ram nothing would happen. It would continue to run in DC. However upon adding the 4th stick, it would force your PC into 2T mode

what is 2t mode?

and would the new ram be in dual channel too? or just the original ram?

lol can anyone help me.

bump