We use a Roku, Netflix, Amazon Prime and You Tube TV. We had Sling TV for about two years but You Tube TV has a much better sports package. Also, You Tube TV has local ABC, CBS, NBC and FOX channels so you don't have to buy a separate Over The Air antenna.
Before cutting the cord we were $220+ for cable and internet at our home (I live in Florida and have Cox Cable).
Now, we pay $80 for internet (including all the taxes and fees), $Netflix (Not sure, think it's like $10/mo), Amazon Prime which we already had and $40 for You Tube TV. Save $40-$50 but get the streaming and ability to use any mobile device at any time.
You will want to verify what speeds your internet provider has and if they have any usage overages.
As far as speed and buffering, I bought a new dual channel (2.4 GHz and 5 GHz) router for $150 at Christmas. I was looking at some of those $400 home internet networks and salesman told me if the devices are getting a signal but it sometimes buffers those wifi extenders aren't worth it.
It is very common in my home for son to have Xbox and laptop running, daughter having laptop and Roku going, wife on Roku and me using something and we don't have any other problems.
We used to use a Amazon Fire TV stick but I switched over to Roku and find it to be better interfacing.