With the data we have, it's impossible to say whether Peter Wirick of Pendleton Co came from PA or went to OH although either/both are possible (perhaps, even more likely than not).
Certainly, two items in the will are of particular interest - the son named David and the wife's previous married name of Johnston or Johnson. We see the name David in the household of Peter Wirick in Pendleton Co. and there was a Johnston (aka Johnson) family in the same area. However, David is a common given name and Johnston (aka Johnson) is a particularly common surname. I can't say whether a Sarah is "missing" from the Johnston family though - maybe someone more familiar with them can help out.
The best bet, right now, would be to find out if the wife Sarah or the older children, particularly David, were born in PA or then VA (now WV). Getting approximate ages for the Peter who died in 1823 and the David, his son, mentioned in the will might help eliminate them as having been in Va (or alternately keep them in the "ballpark").
Due to the internet confusion and the "taking" of the same ancestor for completely different families will probably require that both Peters of eastern PA be worked year by year in their respective counties until one, both or none, disappear from the tax rolls/sell off all their land. Even then, it's possible that neither will be the Peter Wirick of VA/WVa. Some alternate solutions for that Peter would be that he moved to Kentucky, Tennessee, or further south in VA; he moved west or NW in what is now WV; he moved back to whatever area of VA or PA from which he originated (maybe an inheritance to himself or his wife?). All are possible and we currently have no clues to help.
Thanks for the update and please keep us posted with your finds.