Hi all, new CI4 user for my startup

Hi All,
Today, I develop at work mainly with Laravel but at first in my current job I launched CI3 webapp which are still used and enjoy alot working with this code legacy project : simple, maintenable, easy, speed.
Now it's time for me to launch a new project for my business and although laravel offers ready-to-use solutions I prefer CI4 for mainy reasons : 

• Speed
  
• Simplicity
  
• Easy to recrut junior mid level PHP developer and teach them how to work on CI4 in the near future 
  

I have some questions or advice, i want to know the best built-in solutions for : 

• register / user / login system = myth auth ? Or social login auth exists ? 
  
• relationship between models "laravel like" or fuc### this and do differently ?
  
• Stripe intégration, looks like not very hard but if there is some system to integrate easily different way of payment, cool
  

Good WE all CI lovers