When using any chemicals: rule number 1 - never mix them before using.
That means solution #1 and #2 should be added to the tank in a different time (it is stated on the bottle)
Brand of #1 and #2 does not really matter. All of them working in the same way. Just depends how desperately brand owner wants money.
Mg is save to add any time. Mg brand does not matter - it's cheap chemical element, the same for all brands.
Trace elements should follow to rule number 1 - do not mix them. That means they have to be added separately.
That's actually the difference for balling and calcium reactor:
-with Calcium reactor: trace elements are optional
-with balling: trace has to be added or frequent water change is required to add these elements