I have a TP-Link DECO mesh internet system. Roughly half of what the Nest/Orbi/Eero systems cost. I put one puck on each floor of my house (basement, main, upstairs), and it works great, much more consistent signal than with just the router.
There is an app called Wifi analyzer that works very well. For checking signal strength as you move around the house.
As far as speed testing goes, you don’t need the app, the Google SPEEDTEST works as well a Ookla.
Just go to Google and search for speedtest and hit test. Works very well. Ookla has (had) some issues.