Of course Object Editor does lags if it has more than 100 custom abilities. There's a widgetizer tool thing made by Vexorian, I think it will reduce some loading or lags. No if you convert the GUI to JASS, it will make an ugly code and less efficient. Anyway JASS will remove lags if it is used properly, remove leaks and nulled a handles/agents. You must reduce a map size or removed some arenas, because if the map has too many handle objects to take care of, then It will make a lag.