XPS 8900, adding non-Dell RAM, proper slots

I have an 8900 that I am refreshing for family use.  Not looking to sink a whole lot of $$$ into it.

The desktop cams with two 8gb RAM sticks installed in slots 1 and 2.  These slots are not adjacent to each to each other, but they both have white clips.  Slots 3 & 4 have black clips.

Am I correct in saying that even though 1 & 2 are not adjacent, they are in the same channel (“0”?), and that if I add two more sticks into slots 3 & 4, those two will be in the same channel (“1”)?

i ask because the two new sticks will not be Dell, but Crucial.  The specs are exactly the same among all four sticks, and my understanding is that Crucial is pretty good in terms of Dell compatibility.  However, just to be on the safe side, I want to avoid having two different brands of memory in the same channel.