Connection speed has dropped to about 1.5mb/s and remains steady.
Connection speed has dropped to about 1.5mb/s and remains steady.
Interesting - my guess is that it's simply doing a "speed test", which would measure your effective internet connection - this is, however, not necessarily the same as your actual rated speed package. For example, your ISP is extremely unlikely to sell you a "124 Mbps" speed package - it's just an odd number that's not typical. Furthermore if the speed measurement changes at all, then yes it's definitely just doing a speed test. With that in mind, that's a useful tool and not a bad thing at all. Your effective speed is more important than the rated speed (although if there's a large discrepancy, you should complain).
You're wondering if both powerline and WiFi were tested, and whether the powerline issue is affecting your modem's reported speeds. It seems the powerline might be causing interference, especially with DSL connections, which could explain the noise and impact on performance.