"The problem with '100M' is that many websites do not go that fast... :/"
It is not 2001 anymore. There are no servers left with 100Mbps ethernet ports, and if by some miracle some where still operating, replacing them would be cheaper than the electrical operating cost.
Youtube does not limit bandwidth. Due to Google's size, they are everywhere. If they could get you to download more that you already do, they would.
Fast.com is a Netflix tester, and basically stops measuring beyond the speed that Netflix could actually use. On Speedtest I can get speeds of 900+ Mbps, but not on every server as a lot of test servers are still on gigabit ethernet.
After the initial Windows 10 uproar died down, I was able to download the Windows 10 at over 800Mbps peak (took 50 seconds in total). I'm able to get Apple updates at around 500Mbps. It is harder to find something substantial at Google, but Drive is able to do hundreds of Mbps at uploads and downloads.