Hi Rafael!
When adding stakeholders, you can designate them as employee or consultant. This doesn't control any tax implications, the actual equity you issue is what causes tax implications. You'll want to speak with a tax consultant for further information on international tax laws.
In regards to question 2 and 3, Carta will not send out employment letters on behalf of a company. The column for annual salary is more for internal record keeping purposes and is not a required field.
If you have any further questions, please feel free to reach out to launchsupport@carta.com!
Regards,
Support - Chelsie