The platform is named after the firm's cofounder, Marcus Goldman. Internally, it is seen as a startup within Goldman Sachs. The launch marks another step towards consumer retail banking for Goldman, which is arguably the best known investment bank in the world.
Different modems or routers may be more or less capable of working with the weaker channels that are coming down your phone line. If a channel is considered too weak by your modem or router, then it will not be used. So YES, a modem or router can affect your Internet speed. Finally, there is little point in going for a super fast connection if the sites you are regularly using are limited to significantly slower speeds unless you are doing several things at the same time with different sites.
There is no way to limit by profile, but depending on the quality of your router you could limit access by MAC or IP address. If you router offers the feature you should see it under the access restrictions tab or something similar in the administration.