Reddit mentions of (2 Pack) Internal 36 Pin Mini SAS HD SFF-8087 Male to SFF-8087 Mini SAS Cable 2.0 Feet / 0.6 Meter

1. the short answer is no, you can't use the storage slot. The PCIe ID of an IT-flashed card is not recognized and the R710 won't boot with the IT card plugged in it like that.
   
2. These should be good, sorry I don't have a P/N
   
3. Yes, you can use LACP, how to set it up depends on the OS you're using. You can choose to have the iDRAC on the dedicated port or to still use the onboard ones, the former is generally preferable though when you have a physical NIC for iDRAC.
   
4. You got how to fill up RAM wrong. You can use 8x8GB sticks, filling slots from A1 to A8 and leaving A9 empty. It is preferable, if you use both CPUs and therefore can use all the 18 slots, to have a matching configuration across CPUs, but it's not required. In case you still have to get RAM, note that the maximum speed it can operate at depends on the configuration, so it might not make sense to buy faster RAM if you'll be bound to a lower speed due to the machine and lower-speed RAM is cheaper.

https://www.amazon.com/gp/product/B0769FWJJP/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

this is what you want

Does Amazon US ship to Canada? If so, I just put these in my R720xd: https://www.amazon.com/gp/product/B0769FWJJP

You can pick these cables up, https://www.amazon.com/gp/product/B0769FWJJP/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Why are you going with an H200 over the 700? I have an old H200 from a R510 if you want it.
edit I think the h200 is pcie-4 only?, so you can keep it in 3 of the 4 slots on the riser. 3 of the slots are x4 and the back bottom slot is x8.

Here are two internal 36 Pin Mini SAS HD SFF-8087 right angle male to SFF-8087 Mini SAS cable 3.0 feet / 0.9 meter length for $12.48:

https://www.amazon.com/gp/product/B0769FWJJP/

The card I got is "LSI LSI00244 (9201-16i) PCI-Express 2.0 x8 SATA / SAS Host Bus Adapter Card". I got it from NewEgg.
The backplane and the card both use standard (multi-lane SAS) SFF-8087 connectors. The backplane requires right-angle connectors due to the tight fit, so I got these cables: https://www.amazon.com/Internal-SFF-8087-Right-Angle-Cable/dp/B0769FWJJP/

Note that the backplane uses port multipliers to allow 12 drives to be hooked up to 8 SAS/SATA lanes using two SFF-8087 cables (each cable is four lanes). The only issue with this is that the order your system lists the drives in may not be the same as the physical order of the slots, but I have not found that to be an issue so far. It just means you should record the serial numbers of which drive is in which slot so that you can still do hot-swap replacements. It's really just a minor inconvenience.

Also, I have, and highly recommend getting, the extra two 2.5" rear drive bays. ZFS allows you to install SSDs to operate as cache drives, and those two slots are a great place for them. If using the Dell built-in connections, the rear bays hook up through the front backplane's port multiplier, but I ran a third SFF-8087 cable directly from the LSI card because there's no reason to waste the two extra ports on this four-port card.

My data drives are 10x 8TB Seagate Enterprise ST8000NM0055 in raidz6 configuration. I chose them from the BackBlaze quarterly Hard Drive Reliability data. I highly recommend looking there for the most up to date data on drives they use and failure rates. I have 2x 512GB Samsung 860 PRO SSDs in the rear slots, configured as L2ARC cache for ZFS. The OS (I'm using Ubuntu 18.04) is on 2x 1TB Western Digital Black in a raidz1, chosen just because they were cheap.

I am pretty happy with this setup, but there are two changes I plan to see if I can make. First, I am going to see if I can move the OS raidz1 onto two more SSDs, likely M.2 SSDs on PCIe adapters. Second, if I do that, is to put in two more 8TB drives and add them as hot spares so ZFS will automatically start rebuilding onto them if other drives fail.