If you reinstalled Seven over the previous installation, nobody knows what really happened with the remnants.

Running the correct removal utility for your old AVG under Windows Safe Mode has no “cons”. Try that step first and test again your system.

If you want to uninstall Avast and use the uninstaller for Avast, you may try it too.

I don’t know what is causing the slow connection, so the only thing you would waste is some time to download the required files, uninstall, remove, reinstall, configure, some reboots in between, and test.

Remember to run the removal utilities for AVG (and eventually for Avast if it turns to be necessary) from Windows Safe Mode (In theory, not necessary, but in practice, we have seen some conflicts avoided when running them under Safe Mode).

You could also try speedtest.net with Avast active, and then temporarily disabling shields (while, in both tests, any other program should be closed and stopped). But you should know that any difference can NOT be automatically related to Avast itself anyway.

Whatever you do, please report back.