Sim800l info before buy

I have some questions before buying this module:

  • I need the ability to, obviously, send sms messages to different recipients and I need to read incoming messages, precisely to forward some sms if they are from specified senders.

  • I’m using a raspberry pi3 b+ with its power supply, do I need to buy another power supply for the sim800l module?

  • can I follow this guide? SMS and a recommended modem

  • is there a “better” hardware module model to buy?

  • does exists a case to enclose both raspberry and the sim800l module?

Thank you

Related to the guide that you propose (dedicated to ESP), M5stack has a cased sim800l

I know also that A6/A7 module are compatible with ESP.

I don’t have experience related to raspberry pi with GSM modules unfortunately.