I agree, anytime for topping depending on situation; per your setup, I would go ahead and top them. Maybe try out the SCROG technique for this grow?
Also, cutting the light back to 18 or 16 on may help with the heat, too. I could get into the reasoning... ah... why not: Night-time metabolic processes are important and directly related to the structure of the plant. One of those major processes is converting glucose (produced form photosynthesis) into cellulose (a main ingredient in plant architecture - also one of the oldest insulation materials used in constructiontoday; ironic?? hmmm.. lol). In your case specifically, and imo, this will aid against hotter day temps simply by allowing your plants to prioritize cuticle developement and repair; I'm sure they'll respond vigorously.
Yes