Poor equipment can contribute to buffering but really it’s the way you setup your equipment and your internet connection that has a bigger impact on whether you’re having a lot of buffering issues.
I have experience setting up many different devices for people and whether it’s a 1st Gen firestick or a Nvidia Shield, I’ve been able to set them up to run near perfectly if the person that owns the device has a reliable internet connection.
The only real improvements you notice with a more powerful device such as a Nvidia Shield is the ability to navigate quicker, slightly quicker loading times, and the ability to handle smoother playback for much larger files such as 4k links which can range from 30-80gb in size.