For your first question, if this is your 1st box then better spend on newer box with newer hardware. Fyi, Mibox S is still using same hardware specs since 2016.
If u are into online streaming only there are newer alternative like Chromecast with Google TV or Mecool KM2.
Mecool KM2 will be suitable if you plan to use it for local playback.

On the second question, RM17/Month package is only for mobile & not able to cast to TV. You need to upgrade to other package.
Better subscribe to premium package & share with 4 people or join existing group.

Refer here for more details:-