FWIW, I just moved from a 50/200mm F4, to ZWO's 60/280mm F4.6 guidescope.
My guide camera has 3.75 um pixels. No plans to change pixel size.
I was able, with a decently-adjusted EXOS2 and the 50mm, to float between 1.1 and 0.8 RMS, under good conditions. Mine is all-cables, no wireless. I wanted to be able to be consistently sub-1.0 RMS, conditions permitting, and Jerry's advice to me was to go longer.
I did that, and it worked. But it is a tradeoff. The good news is that round stars for longer exposures became more dependable. But. The price of that was that the increased guiding resolution made PHD2 fussier and (for me, anyway), less set-and-forget, and more drive-according-to-conditions. Basically, I increased PHD2's ability to chase the seeing and it requires a bit more work to settle it down. But I'm sticking with the ZWO. :-)
My scope is 621mm FL, vs your 750, and my D5300's pixels are 3.95 um, if you want to plug those into Wes's formulas for comparison. The D5300 works fine with BYN, just watch the USB cable - it's 'special', and you may need to buy Nikon's in order to get enough length.
Hope this helps.
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras: Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer: Thinkpad x230, Win7Pro/64