I agree, I'd probably use it too. So long as they WORK together, then it's usually ok. It's just that OFTEN, they WON'T work together. So long as they do, no harm no foul, mostly anyhow. I'd always rather see 2 x16GB for a 32GB memory configuration than 4 x8GB, but sometimes you play the hand you are dealt.
Yes, I would absolutely run them at their XMP profile settings. You'll need to set the XMP profile setting in the BIOS. It's not terribly hard. This guide should tell you everything you need to know about how to do that and I'd recommend you read it, several times if necessary, and try to set the XMP profile. As I said, with four modules you MIGHT need to slightly increase the DRAM (Memory) voltage as well since four modules at high speed tend to often not want to be stable with the default XMP settings, BUT, they might, so try it and only worry about the voltage if they don't want to RUN properly.
If the system doesn't want to POST after allowing it to try several times (It will probably restart itself two or three times while training the memory) then power off, take two sticks of memory out, power on, go into the bios, find the DRAM voltage setting and increase it by .005v, save settings, exit the bios, power off, install the other two modules back in again and try powering it on again to see if it will POST.
If you are not comfortable with doing this then I'd suggest you find somebody who is familiar and trained in doing this, like a shop.
*Resolving memory problems and setting up XMP/DOCP/AMP profiles