Just to say have not purchased it yet 
have asked first
good luck
I recall the fact that WDS was unable to work a year ago when I was using the same type of MT7620A router.
I don't know whether this problem still exists.
finding a good (cheap) device is like hunting a unicorn 
@robimarko
It seems that I am not dreaming.
Https://bugs.openwrt.org/index.php?do=details&task_id=896
There are reports in July that ASUS_RT-AC51U has not been spared.
This problem usually appears as follows
There is approx. 50% chance that AP stops receiving packetsi mmediately from all clients after sudden client disassociation under heavy load.
And the kernel log is filled with the following content
[19391.285334] ieee80211 phy1: rt2x00queue_write_tx_frame: Error - Dropping frame due to full tx queue 2
[19391.303739] ieee80211 phy1: rt2x00queue_write_tx_frame: Error - Dropping frame due to full tx queue 2
[19391.392292] ieee80211 phy1: rt2x00queue_write_tx_frame: Error - Dropping frame due to full tx queue 2
[19391.410769] ieee80211 phy1: rt2x00queue_write_tx_frame: Error - Dropping frame due to full tx queue 2
[19391.429200] ieee80211 phy1: rt2x00queue_write_tx_frame: Error - Dropping frame due to full tx queue 2
[19391.447617] ieee80211 phy1: rt2x00queue_write_tx_frame: Error - Dropping frame due to full tx queue 2
The final report was two days ago
By the way, if you search for rt2x00 in this forum, you can find something more exciting.
the version 13 is a 64 meg ram 8mb flash device based on mt76?? mediatek ralink something or other. did they ever get that driver working? i have a version of openwrt on it but it drops connection like crazy. cant get it to flash back because i need a stripped firmware and the EU version is the only one i can find and it doesn work. you are supposed to take the first 200 bytes out of it or some dang thing