[jukx]

Sure, here you go:

frame:RegisterEvent("UNIT_TARGET")
frame:HookScript("OnEvent", powerBarHandler)
 
function powerBarHandler(frame, event, unit)
    updatePowerBarVisibility(frame)
end
 
function updatePowerBarVisibility(frame) 
    local unit = 'target'
    if UnitPlayerControlled(unit) or UnitPowerType(unit) ~= 1 then
        frame.Power:Show()
    else
        frame.Power:Hide()
    end
end

(simplified a tad)

The goal was to hide the target frame power bar for NPCs that don't use power. From testing it seems that they have assigned the power type 1 (i.e. 'RAGE').