Internet Download Speeds

I take it you have the orbi RBK753?

Your wired is the speed you'll get as the 7 series only has the gigabit ethernet port. that 940mbps (ish) is what it'll max out at unless you upgrade to the 8 or 9 series. 

wireless speeds are much more variable. the maximum link speed you'll get from the 7 series is 1200mbps as that's the 5ghz fronthaul it uses in a 2x2 configuration. Again, that's link speed. throughput tends to be around 55-65% of link speed from network overhead/efficiency as Mikey94025  already pointed out. Plus 5ghz distance drops off quickly. I've seen people hit around that 800+mbps over the 5ghz fronthaul but that's right next to the router without any interference. Add interference/distance, and that 400-500mbps is much more realistic for speeds. 

Your satellites are another subject. You might not get the same speeds from them if you're using the wireless backhaul as distance/interference/obstructions can slow that down. so its harder to predict. But I would recommend trying several different locations with the satellites. they should be at least 30 ft apart for roaming to work properly. but try several spots for each satellite because things in the walls/environment (think hvac or certain appliances) can block wifi very well. And sometimes moving a satellite from one side of the room to the other, removes that obstruction and can make the satellite work better. I usually tell people to grab a laptop and connect to the satellite hardwired so when you're positioning, you're just testing the backhaul. When I first moved to a mesh system, it took a couple months trying different configurations of how many satellites and what position to run them in. I've figured out what configuration is best if I'm using 2/3/4 satellites in my home through a lot of trial and error. Plus I just like to optimize. So try different things and test to see how they work.