I recently purchased a triple E4 set to get better wifi experience though out my home. 3 Floors, concrete walls/floors, terraced house.

We can expect MAX 120 mbps as per our ISP, normally get 80/90 wired on ground floor. That is why I did choose the E4 (Max 100).

Wifi at ground floor around 25Mbps, 3rd floor now is 1 - 3 Mbps ... I can't work there.

I was able to buy 2 additional  E4-DECO's for a very reduced price,

My question 1: when I experience not enough coverage/speed on the 3rd floor, is it ok to use the 4th and 5th DECO in my network as well, or can I expect issues/reduced speed

when I do? (the more DECO's, the lesser speed?.

Question 2: on all set-up DECO *whatever the room it is in* I can connect a laptop (wired) in order to work from there and will the speed be the same as the wifi-speed?

Question 3: I read 2,4Ghz reaches longer distance in the house, but 5 Ghz is more stable and better ... Can that be a reason to use all 5 DECO's and put them on 5Ghz?

Thanks for any helpfull reply!