What I wrote above pertains to the 2.4G signal, and if one has a dual-band router, the 5G signals can also be examined with WiFi Analyzer. We use the 5G signal on our mobile devices since we have good coverage for it in most of the house and we do a lot of streaming; 5G is essential for that. In fact, I don't even use the 2.4G and have told my personal devices to "forget" my 2.4G signal, but if I need it, I can always get back on it by entering the password again. Only our Chromecast and Echo use the 2.4G, because in the Echo's location, 2.4G is stronger than the 5G. Since the only streaming the Echo does is music, 2.4G works fine since music streaming is lots less demanding than watching HD video on tablets.
The main Guest signal for internet-only also uses our 2.4G, and if I want to allow someone into our home network, I have another Guest signal that uses 5G and allows for accessing our home network's media files. The second Guest signal is only on for when "special" guests are visiting.
One other tidbit: When I got an Amazon Fire Stick and connected it to the 5G, I noticed that the Speedtest.net results had dropped significantly. So, I connected the Fire Stick to my range extender's 5G (with a different name) and the Speedtest results on the main 5G signal returned to normal. Seems that if the Fire Stick was streaming on the main 5G it degraded the signal, but on its own signal, 5G_EXT, it did not.
Wireless can be weird and strange, and why I use wired connections when and where I can with my many gadgets, computers, etc. Fortunately, my house is CAT5e cable wired internally in many rooms.