Range Extender

 Hello  @Taff 

Q3.6: Can I use more than 1 range extender in the house?

Most frequently asked questions about TP-Link range extenders

If you have 2 range extenders, please try to connect  both range extenders to the router directly.

It is not very recommended wirelessly connecting one extender to another, as the performance for the second extender could be unsatisfactory.
Topology : RE1 )))(( Router )))(( RE2

Or you could consider using one of REs as AP mode (wired to router or front end):
Topology:  router )) (( RE1 <Ethernet> RE2 (AP mode)  this requires RE supports AP mode.