PS4 Wifi issues and how to fix them?

Okay, so I'm late to the party.

This post is essentially a plea for help. My network provider has speeds up to 100mbps, and I get around 70mbps on my phone, with a ping of 16/17.

However, when I run a speed test on my PS4, it gets maybe a tenth of that download speed. Is this a common issue?

Lastly, I'm thinking of buying an Ethernet cable to run from my router downstairs up to my PS4. Does anyone know what the different categories are in regard to Ethernet cables and what's the best to buy?

Thanks