For Apps, the only thing that is restricted is that you cannot delete the app unless the owner is changed (I believe that this can be done in PowerShell, but have never done it). It is much easier for the new owner to use "Save As" and change the owner on the new copy. All co-owners can edit the app.
For a Flow however there are some things to watch. If the Flow is triggered from Power Apps, the same as above applies (as the connection is the one of the user), but saving a copy will mean re-connecting the new one. If the Flow is triggered by something else, you have a problem as it will break the moment your account is deleted. It is however not a big job for a user the Flow is shared with to edit it and change all the connections.
All of my apps and flows are owned by a service account for this reason - when I leave, I simply relay a password and user name.
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