We’ve just been discussing these issues on another project, so you should find the following thread interesting. That project faces different challenges from years, but the basic issues in a big multifloor house are the same.
One of the main caveats is that if you boost the Wi-Fi signal in the 2.4 band, you create interference for your zigbee devices. And many boosters automatically boost the 2.4 when they boost the five even if you’re not using the 2.4. (Plus I think echo only uses a 2.4, doesn’t it?)
I have one room in my house where if I put the Wi-Fi booster on the west wall, we lose all the Zigbee devices past it on that side of the house. But if I just move it to the opposite wall, everything runs fine.