I have a 2865 with separate 2.4 and 5 gHz SSIDs.

There is weak WiFi at one end of the house so I bought a Vigor AP 802 to extend this.

I don't really care what mode it works in as long as it extends the WiFi but I can't get it to work at all.

I have the Draytek Wireless app but that doesn't seem to do anything and the instructions that came with the 802 are next to useless.

How can I achieve what I want to do? Is a mesh network by best option?

When you say you can't get the 802 to work can you be a bit more specific?

The instructions in the user guide seem about as comprehensive as most Draytek instructions to me, setup seems straightforward enough (disclaimer - I don't have an 802, but I have had many Draytek AP's over the years)