Re: #1 - It places "some" remediation in Microsoft's remit, plus you get better insights/input into common failures/remediations seen in the global community when they installed those updates. Also, the forced cadence makes conversations with customers easier.
Basically for physical devices,
-> M365 uses Test&First/Fast/Broad over a 0/3/7 day deadline; released on Patch Tuesday.
-> Edge uses Test/Remainder rings using Beta/Stable channel released weekly and monthly (depending on update type).
-> MsTeams doesn't use Autopatch rings and my understanding is the update channel and cadence cannot be controlled. ie Autopatch doesn't change MsTeams update behaviour.
Re: #3 - Yes it does drivers. That cadence is covered here.
Be mindful that Autopatch behaviour is different for VDI.
Keen to hear from others on their input on these questions too though.