In my tests, updating the priority of a project created a journal entry without a scope value, but updating the priority of a task created an entry with a scope value. Therefore, you should be able to filter "Scope is blank". I did not need a Change Type rule to return the correct list of entries.
fieldName=priority
fieldName_Mod=cicontains
entryDate=$$TODAYb-2w
entryDate_Mod=between
entryDate_Range=$$TODAY
objObjCode_Mod=isblank
project:status=CUR
project:status_Mod=in
If your JE reports aren't returning any results, you should confirm in Setup > Interface > Update Feeds that you are tracking Priority for the Project object.
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