1. You configuration is ok. 70dB is good enough.
But it would be better to configure the second TL-WA7210N as Client mode instead of bridge with AP mode. Bridge with AP mode will lower down the wireless speed between the two 7210..

Other suggestions:
on the 1st unit, AP mode, 11n only, channel auto, WPA2-PSK security, AES encryption, 8dbm output power.
on the 2nd unit, Client mode, 8dbm output power.

2. The speed test tool on the management page is not accurate, it is based on delivering ICMP packets. So don't be too concerned about that result. To find out a more accurate result, you can try Iperf or just copy a big file between two computers.

Also, you current result is not bad at all. 22Mbps is the speed rate on application layer, which co-responses to a wireless speed of 50Mbps~ 80Mbps.
After all, we should realize that WLAN is shared-media. the radio channel resource is too limited in the 2.4GHz band. Your neighbor's WiFi networks around you also share the same limited channel. Like driving on the road, everyone just cannot enjoy the wireless speed alone.

For your reference: http://kb.netgear.com/app/answers/detail/a_id/19668/~/differences-between-link-rate-and-transfer-speed-and-throughput

fotodamaris wrote

yes, this is what the book says, but 50m away is not a distance to be concern, the concern should be the 7210s this devices came out with flaws, its posted here, http://forum.tp-link.com/showthread.php?59935-TL-WA7210N-Channel-bandwidth-and-rate you wont see the whole thread cause @danymarc is on transparent mode by the Admin.
other flaw, came out without Ping Watch Dog, later they added to the menu. but it does not work, after days of work drops wifi, reboot need it.

Thanks for your reply. I've seen this thread already. My Device has a S/N starting with 214136XXXXXXX, according to the posted thread this should be not affected. However I actually do see the connection dropping and only a reboot helps. Are all 7210N affected by this? Is there a way to get a replacement unit?

fotodamaris wrote

Have you follow @tobacco suggestion on post #2

Yes, I've updated it today and so far everything works. I will have to wait a few days to see if its better now.

cheers, karim