External users questions

Hi,

I´m trying to figure out all about external users.

Is there a setting so that they can see information about people in the organisation in people webparts?

If they need to create a microsoft account is it possible to name that account they same way as there own email? Example, if a user have abc@gmail.com can the microsoft account be the same. I mean, does the microsoft account being created in the background?

I´m really worried that I will scare our customers away if I force them to create a totally different account.

Thanks in advance