VPN questions from a noob

I just discovered Kodi and I have read that it is recommended to use a VPN so that the ISP doesn’t throttle back my service. I have 2 questions:

1. Will adding a VPN to my Firestick affect, in any way, any other computer that is in my wifi network?
2. And, I see there are choices on VPN on who to use. What is the best way to go ?

Thanks!