i really only need Inline editing for 1 permission set on a custom object
i'm working on,is this only at the Org level?,
so if it's enabled everyone will see it
and on all objects?
Yes,this is an org configuration. However, there are few more considerations like profile edit permissions, etc.
Check the following article for more details. https://salesforcethinkers.home.blog/2019/09/10/inline-editing-in-salesforce-mass-edit-records/