Good job. If you would like to simplify it a little, you can do just this:
Lua Code:
local ShrinkNameplate = CreateFrame("frame")
ShrinkNameplate:RegisterEvent("PLAYER_ENTERING_WORLD")
ShrinkNameplate:SetScript("OnEvent", function()
C_NamePlate.SetNamePlateFriendlySize(60, 30)
end)
Since you only have 1 event registered to your frame, you don't have to check to see which event just fired. And since you are not using any of the arguments passed through to your OnEvent function, you don't need to save them to any variables. Lastly, you don't need to give your frame a global name, since you won't be accessing it outside of your addon.