The point is if it's stable or not. Also if there are other devices connected to the same wifi. That will eat up bandwidth.
I have 29mbit which is very steady and have no problems with
Netflix, Amazon or youtube
Another option is to go for the new shield tv, while not perfect, the ai upscaling is supposed to be decent.
Most 4k content is about 14-17mbit, it's when it's HDR that would be the problem as it goes above 20mbit.