Maybe. Maybe not. If you buy a set of the exact same RAM and mix and match it might not work. Don't know until you try it. You will be limited to there slower speeds, maybe even default DDR4 speeds though because you can't run them at different speeds and timings.
I was hoping one chanel would be 3000, the other 3200.
If they both run at 3000, just how much effect would this have, is there really much difference running at 3000 vs 3200 on a non gaming PC. I do quite a bit of video editing ?
More the risk you take is that it won't even run at 3000 and you have to try the base ddr4 speed of 2400. Even though it likely will run mixed memory at 2400 there are no guarantees.
The example/benchmark they use to show difference in memory speed is a application like ZIP file compression decompression. Not sure about video editing. For almost all application more total memory makes far more difference than the speed of the memory. Most people can not actually tell the difference between memory clock speeds unless they have some kind of testing tool running displaying some number on their screen.
1. always use the same brand
2. never mix different Mhz because the lower one will pull down the performance of the higher one.
3. consult your mobo manual for which slots you should use in relation to how many sticks of ram you are using.