I have a peplink balance one core and my internet speed is 1gig in download and 50 Mbps in Upload. When I do a speedtest (att speedtest, speedtest.net, rogers speedtest) I cannot get the speed I mentionned above. I used a mac and it is connected with an ethernet cable to the router.
It is also good to keep in mind that the speed tests using external test servers are subject to whatever constraints they encounter on all the connections between you and the server. That may (or may not) be relevant to your tests. Furthermore, how you run your speedtest may matter - standalone app, as a browser app, as a connection to a site, etc.
For instance, we have one (currently idle) server connecting via a 1.5 Gbps router to the world. And yet speedtest.net (accessed on Safari) gives us a result of 680/230 Mbps (down/up), accessed as an app gives us 750/480, and testmy.net (in Safari) gives us 99/73 (!).