LawPhoenix

so "bootleneck" calculators are a bunch of BS.
it comes down to games, programs and whatever else you want to do.
your 6 core will be faster than a 3700 in any multithreaded program.
a 3770 maybe better if all you play is games from 2014 and back but newer ones with a few stupid exceptions (far cry) run much better on the 6 cores.

Funfact, many vendors use the same factories, so if you strip a few different rams from separate vendors of their heatsinks, some of them will look exactly the same. 

As long as the system is stable, then yes, you can run different brands in dual-channel. The claim that they need to be "specifically programmed to work together" is just plain bullshit.

Should work fine, usually the motherboard will run at the speeds of the slower stick for compatibility

You could mismatch any kit and still run dual channel, just be aware that you may be limited to running lower JEDEC specs (e.g. 2133MHz CL15) for stability's sake

Yes, if you have the modules in the proper slots for dual channel, and the system is able to POST, it's running in dual channel. As far as your timings are concerned, the faster module in whatever respect will automatically back down to the slower module, including latency.