In that case then, is 50mbps enough for me to play League of Legends with constant ping and at the same time can 2-3 members of my family use the internet to browse instagram/facebook etc.?This is ask the second ISP. It all depends how many wires come into your house from the street. Most houses have 4 and normal dsl uses 2. To get 50mbps many times they use VDSL which needs 4.
It will me messy to use 2 ISP at the same time you can do it but unless you can plug different devices into different routers it requires lots a careful configurations.