During my training session with Power Apps, I'm often asked if you filter the records shown in a gallery to only show based on either who created the record or who the record is assigned to. The simple answer is "Yes!". To do this, however, there are a few things to keep in mind.
1) In your data source you will need a column that contains some kind of identifying information of who is assigned the record.
2) If you are filtering based on email addresses you could run into a delegation warning.
3) You can filter your records either based on the currently logged-in user or by having a drop-down selection of the individual email addresses/identifiers assigned to your record.
Take a look below and how this can be accomplished in your app.