First build with a few open questions

[cloudycelt]

not offhand, no. I would have to rtfm. except I'm not buying it so I don't wanna make my eyes bleed to read it for you. supermicro is usually pretty good for putting a block diagram that shows the exact layout electrically, which should answer that question.
boot will only be used on....boot, and small changes to config (basically a bit of text), and will have functionally zero bandwidth usage.

Ah sorry if I was unclear - I know that they do indeed share the bus, that wasn't what I was wondering about. My question written better would be "Given that I have two slots that share the same PCIe x4 bus, would it be alright to use them potentially for boot & SLOG?"

With you reply above you've essentially answered the question - since boot itself has relatively super low performance impact it sounds like it would be just fine.

 

[artlessknave]

ya, it should be so low that I'm not sure you could even measure it.

 

[cloudycelt]

ya, it should be so low that I'm not sure you could even measure it.

Perfect then, I think I'm pretty much set in that case. I appreciate yours and IQless' advice greatly, thank you :D