I've been doing a lot of testing to ideally place my eeros (I have three, 3500 sq foot house, two levels and a finished bedroom in the basement).  My Internet is Verizon Fios with 500/500;  I have the gateway eero connected directly to the Verizon ONT (i.e., no other router is involved). 

Here are some of the issues I've been having:

1). If I'm in the same room as the gateway eero, I get decent wifi speeds, running the Ookla speed test.  My averages are in the high 400's for both up and down.  If I plug in to the eero directly, I get over 500 up and down running the same speed test.   If I move one room away, I'm still averaging 300+ up and down.  However, if I connect to a leaf eero, I seem to be maxxing out at 150 up/down; similar issue on both leaf nodes.  Both show an "excellent" signal strength in the eero app (5 green bars).    Any idea why this is happening? 

2). On my iOS devices, they often stay connected to an eero on the other side of the house as I move around.  I'm not sure why this is; if I disconnect and re-connect they will generally properly select the best signal.  I've observed this a lot as I test (I always make sure to disconnect and reconnect from the wifi before testing for this reason). 

I might just buy one more and hardwire them, but doesn't it seem like the performance should be better?  I do have a lot (35-40) devices connected at once, but most of them aren't actively doing anything 99% of the time (thermostats, smart lights, etc.)