Ultimately, no one can answer this.
Memory is sold in packs for a reason, and only the memory modules sold in the same pack are guaranteed compatibility. This is because the manufacturing process for the modules change frequently and sometimes substantially. So theoretically you could have 2 of the exact same memory modules, but from 2 different packs, that don't behave well with one another.
This is why manufacturers only guarantee compatibility in the form sold (from the same pack). Making sure that they are the same model, or timings, or latency, is just a way of trying to minimise the risk, not eliminate it.
I'm not saying it never works, it's just a gamble, and the last thing you'd want to do, is spend a lot of money, to find out they don't work well together. This is also why modules in the same pack are slightly more expensive. The same logic applies for upgrading your current RAM.
They can run in flex mode, but the 3200 will likely downclock to 2400.
So no one can answer if they will work, because even if someone had exactly the same models running in a near identical system, in reality, nothing is identical, every system and module is different - even only slightly.