My home network is four Deco M9 Plus  units all hardware version 2.8 all are wired backhaul except the last one of a branch
My network has provided years of rock solid, speedy,  flawless service  and that includes right now.

For the cost of beer money I can acquire  three  additional M9+ units all hardware version 1.1

I don't "need" any of the additional units but for a price this cheap I thought I would extend my kickbutt wifi network down into the basement and out into the garage.

My questions are:
* are there any issues with mixing / matching  hardware units of hardware 2.8 with 1.1 in the same network?

* prior owner made no effort to update firmware of their units. will I have any issues adding old firmware units into my existing network.
* will the deco app have any issues doing "firmware updates" when hardware versions of various units are different?

* will increasing the number of nodes in my network from 4 to 7 cause any issues
(to help you answer this please know throughout my network any 2 decos are always separated by at least a drywall construction closet wall)

Are there really obvious questions I should have asked but failed to do so ?
thanks.