(1) Permissions works as follows: you need to set who has each permission. If you set just tiki_p_admin_trackers to a group (mangers), but no other group (managers or one from lower level which is inherited by managers), then users from the managers group don't have the permissions to see tracker data, etc. (tiki_p_view_trackers_open, pending, closed, insert items, etc.).
So I guess that for what you say, neither registered nor managers have those permissions granted. With admin permission on trackers is not enough, afaik.
(2) perms. on menu form: you can set that only those users beloging to groups which have that specific permission will see that menu option/section, etc.
And finally a request:
Please, would you be so kind to update the Documentation pages to include this information?
(explained with your own words if needed, so that new users understand it as you would have liked it to be explained)