I’ll leave others to advise on Counties Leitrim & Meath.
As far as the Hughes family in Newry is concerned, do you have any townlands (addresses) for them? What were their names, occupations, and roughly when did they leave the area?
Do you want to share the family story that you refer to in case we can suggest what enquiries you might make about it?
The surname Hughes is pretty common in Co Armagh. In Griffiths Valuation (1864) there were 837 Hughes households, though when you narrow it to the civil parish of Newry it comes down to 6. Probably worth adding that part of the parish of Newry is in Co Down. There were another 18 Hughes households in that part of the parish in Griffiths.