Potential RAM Issues?

[BiomeBuster]

So I'm going to buy more ram for my rig. On pcpartpicker it shows no compatibility issues, but I got to thinking. Should I keep the 8 GB ddr4-2666 in slots 1 and 3 and put the Team Vulcan 16 GB ddr4-3000 in 2 and 4? My mobo is an msi z270-A Pro ATX. In case looking at the specs list will help, here it is
https://pcpartpicker.com/user/Biome/saved/ I'm not sure if I should put the new ram in 1 and 3 and the old ones in 2 and 4, let alone if they'll work together (because ram likes to be picky), or if I should keep the old Ripjaws in 1 and 3 and put the new ram in 2 and 4.
Thanks for reading and responding!

 

[scout_03]

they wont work without issue not the same case and same working voltages avoid them or get new one in only if they are on board qvl list .

 

[BiomeBuster]

they wont work without issue not the same case and same working voltages avoid them or get new one in only if they are on board qvl list .

I don't quite understand

 

[scout_03]

check specs of both ram on there maker link and compare you will see .