I have 2 tl840n, 1st as main router on the 2nd floor and the 2nd one on the 1st floor currently running AP mode with ethernet cable bridging the main router to the WAN port in the 2nd one.

I wonder how each mode behaves and which mode should I use between AP VS RE to make extended wi-fi coverage and less hassle connection, with ethernet connection to the main router regardless which mode

ps : by less hassle I mean lessening / removing the hassle to manually connect to the better wi-fi connection between 1st and 2nd floor