Slooooow Internet - Time Warner Internet

This question is about "Slooooow Internet", with Time Warner Cable internet and apps. I'm paying for the ultimate internet service in NW Ohio and its supposed to be 50mps, on its best day its 30mps as tested by the Okla speed test app. But even at 30mps, will multiple devices connected to my WiFi slow down the speed shown during my speed test? I did a test earlier today and got 30mps, again a few minutes ago and got 14.88mps but there's a few people here and 2 are playing PS4 and there's a TV watching Netflix. Is the 14.88 a result of the extra people or am I getting the 14.88mps no matter how many people are on it?

This topic covered Slooooow Internet, and TWC cable internet service.