Couple things.
Yes. You can run the 7i76 and the 7i77. You need the correct bit file (think firmware) in the 7i92. Looks like there is one.
7I77_7I76D is a configuration intended to work with a7I77 six axis analog servo daughtercard on P2 a 7I76 daughtercard on P1
You are going to need rt_preempt realtime kernel to run mesa Ethernet hardware. (The current livecd is rtai realtime kernel.).
If I where you - I would use the new livecd for linuxcnc that has the latest Linux (Debian stretch) and the rt_preemp kernel.
(We need testers )
Index of /testing-stretch-amd64-rtpreempt
Laptops... Hit or miss. I have actually had good luck with rt_preempt on laptops (vs rtai). But you will need to test. Remember to research isolcpus (for isolating cpu cores for real-time).
Linuxcnc is not a buffered system. The computer is communicating with the mesa card in real-time. 1000 times a second every second.
Sam