I remember my uncle just buying a cheap android tablet and flashed some image on it he found on a Russian website. He connected it with a USB cable to the car somehow, he mentioned it’s connected to the CAN bus and he could get some information from the car into that tablet.
But what you are asking is a bit different, you want to have the phone ui on the car, for that, it’s a bit more difficult.
Speed should be the same (as in ping), the bandwidth is half of it. If you are alone 50Mb/s should be more than enought for people who don’t need to download huge amounts of data quickly.
So if you don’t build operating systems from source code, don’t need to download huge games on a regular basis, don’t work as a editor with huge video files you share with others, don’t do p2p pirating, and similar things, I don’t think you will see a big difference.
If you’re a big family where everyone starts streaming youtube or twitch/netflix or do alot of voice/IP calls when they come home at the same time, then you will feel the difference.