The 833A is a good choice. If you can wait just a little bit longer, I've heard the 1224A will be out soon. It's similar to the 833A, but it's 12MP and has a much larger field of view if that interests you. Oh, and it doesn't have zoom, so it depends on if you want that or not. (personally I think zoom on a stationary cam isn't very useful)

As for 16ch vs 8ch NVR. I always recommend to go with the 16ch if it's within your budget. We see people in here all the time saying that they never thought they'd want more than 8 cameras so they went with the 8ch, only to be wrong and regretted it. I'm one of those people. Be aware that even though you're not connecting the cams directly to the NVR, it can still only record 8 cameras. That's why they call it an 8 channel NVR, not an 8 port NVR.

As for a Synologoy NAS, you could even use that as your primary NVR instead of the Reolink one if you wanted. They have a package called Surveillance Station for that. Or if you just want to use it as a backup to the Reolink NVR, Reolink supports saving to FTP, so you should be able to save raw footage to the NAS that way.

When it comes to switches... that one would be just fine. You just need to make sure a switch has enough total power budget (which that one does). Most of their cameras use no more than about 8W. Some of the exceptions to that are the bigger PTZ ones like the 823A or ones with big lights like the Duo Floodlight.

There are other lesser-known and cheaper brands that folks here have had good luck with like Mokerlink or YuanLey.

Managed vs unmanaged... most people just go with unmanaged. You'd only want managed if you want to do things like create a separate VLAN for your cameras, or other advanced things.