Sharing a list with external users and granting permissions

Hi All,

I would like to share a SPO modern team site list with external users.

I can go to the list and hit the share button and enter emails.  the only options are View or Edit.

Questions:

1) can I create a custom permission for sharing?

2) How can I see these external users that have rights to the list?

     a) I went to admin.miscrosoft.com and went to the "Guest Users" but none of the share users are               there

     b) I checked the active users, where I see external users, but none of the users I shared the list with.

3) If I share a list externally, what else can the user see on the site?

TIA,

Joe