My Model is the AC750 i believe. I saw on another thread I now can't find (thanks to this clunky forum) that renaming your network does improve the speed of the extended connection and i've found this

One T-P link router is linked to the original router supplied by my ISP next to each other in the same place. Extender RE 200 is placed near to my P.C away from routers. When tested ,ookla shows lesse