Ello Johnny.
1. A VPN is similar to a bridge with lanes. It doesn't matter how fast is your car, a bridge can only fit a certain number of cars in a lane at the same time.
What you should get from this shit ass metaphore is that VPNs have speed limits, which is the internet connection of the server itself to the internet. If it's higher than your internet speed, you're good to go. If it's lower, your speed will be limited to said VPN speed.
Free VPNs tend to have a lower speed cap, while others have better speeds. They can vary from 4 to 77mbps (example values) depending on the provider.
2. VPNs offer an IP that's shared with other users.
I'm not sure about the odds of having someone on that same network play on skial, but yeah.
You will NOT get banned for using a VPN/proxy if your profile is public and you have more than 10 hours in tf2.
This does not apply if the IP is linked to a hacker, in which case any accounts will get permbanned automatically.
3. You can either make your own VPN server at home which is relatively hard to setup, or just get an affordable paid VPN from a provider and set it up (it's relatively easy, and using it takes no effort once the setup is done).
You can also get a VPS and turn it into a VPN (that way you'll have your own IP) although this requires intermediate tech knowledge.
Cheers.
fuck how did I have the energy to type all this