[Nikita S. Doroshenko]

I'm new in programming, so I might be wrong and my code can be too massy, but i tried to replace OnUpdate with C_Timer.After(0.2seconds,function). And on my PC i got 30% less CPU usage of this feature with 30 FPS capped (i used ChocolateBar+libQtip+BrokerCPU to track performance). i think for players with 60+ FPS the difference in performance will be more significant.

local CoordText = WorldMapFrame.BorderFrame.TitleText
local update, frame
 
local function WorldMapDetailFrameUpdate_OnHide()
    update = false
end
local function WorldMapDetailFrameUpdate_OnShow()
    update = true
end
 
function WorldMapDetailFrameUpdate(self)
    if not frame then
        frame = self
    end
    if(WorldMapScrollFrame:IsMouseOver()) then
        local scale = frame:GetEffectiveScale()
        local centerX, centerY = frame:GetCenter()
        local width, height = frame:GetSize()
        local x, y = GetCursorPosition()
 
        x = ((x / scale) - (centerX - (width / 2))) / width
        y = (centerY + (height / 2) - (y / scale)) / height
 
        CoordText:SetFormattedText('%.2f, %.2f', x * 100, y * 100)
        CoordText:SetTextColor(0, 1, 0)
    else
        local x, y = GetPlayerMapPosition('player')
        CoordText:SetFormattedText('%.2f, %.2f', x * 100, y * 100)
        CoordText:SetTextColor(1, 1, 0)
    end
    if update then
        C_Timer.After(0.2, WorldMapDetailFrameUpdate );
    end
end
 
WorldMapFrame:HookScript('OnShow', WorldMapDetailFrameUpdate_OnShow)
WorldMapFrame:HookScript('OnHide', WorldMapDetailFrameUpdate_OnHide)
WorldMapFrame:HookScript('OnShow', WorldMapDetailFrameUpdate)

If you can make my code even run faster and looks better, and point on my mistakes, i will very appreciate it.