Well, for starters, the exact idle rpm would be a function of the carb choice to a certain degree, don't sweat that, set the idle high enough that it won't die and low enough that it won't grab the clutch.
As far as the slides go, you already have them so try them and see. Inside the carb there is a emulsion tube that runs vertical with holes in it, the different slide shapes are trying to reduce vacuum (increase pressure) on that tube by slowing down the air velocity at 0-30% throttle give or take. Reducing the vacuum causes less fuel to flow.
Based on your temps it sounds like you're already tuned pretty well, at low load the temp will definitely drop. Head Temp isn't really a good tuning tool the way you're talking about it here, it's only a warning light duty something being way wrong.