> checking my speed

How?

Note that in order to see "200" (among other things) the source must support at least that speed in their sending of a file.

So if slowdownloadsite.com only sends at 20 MB/s, you'll never see 200 from them.


> I see advertised the devices to plug in throughout your residence to increase speed

What are these devices?
(Sounds like snake oil to me.)