Media Bridge setup

[canufrank]

I've read a few reviews/articles on SNB (like these ones http://www.smallnetbuilder.com/wireless/wireless-features/32238-ac1900-innovation-or-3d-wi-fi & http://www.smallnetbuilder.com/wireless/wireless-features/32320-is-ac1900-worth-it?start=1 & http://www.smallnetbuilder.com/wire...st-look-netgear-r7000-a-asus-rt-ac68u?start=3 by thiggins [which mostly don't have their own threads])

They are fairly dated, but both refer to an inability of most wireless clients to capitalize on AC1900 (or later) throughput. In either case, I can't find any information on what the best method for creating a wireless bridge that is "fully capable of maximum link rate" except for the following:
- maximum throughput can only be achieved in 40 MHz bandwidth
- the router and the media bridge should be 6-8 feet apart (I'm unsure if this was forced by the test chamber)

1. Are the assertions still the case? (the articles have not been updated, nor followups published afaict)
2. Are my 2 inferences above still correct?
3. Can the media bridge be ANY AC1900 or is it recommended to match the router's brand?
3. Is 6-8 feet the optimum distance between router and media bridge? Why?
4. Are there pitfalls to forcing 40 MHz (over 20/40)?
5. What other factors come into play?
6. Is there further reading I should be looking at?

Thanks!