I've been controlling the temperature of the beer during active fermentation with a swamp cooler to keep the yeast in the temperature range I like for the beer being brewed and to prevent fusel alcohols from being produced. Fusels will be produced with hot fermentations. "Hot" depends upon the what the optimum temperature range is for each yeast.
I've begun maintaining the highest temperature reached during active fermentation to make sure maximum attenuation is achieved in the primary. I've recently had a problem with highly flocculant English strains not fully attenuating in the primary. Haven't had this problem with American strains in the past, but will make it a standard practice with all yeasts. I maintain the heating only until final gravity is reached. I'll let the beer cool off to the ambient temperature until bottling day.
The room I ferment in has an ambient temperature of 66°F this time of year. Heating the water bath of the swamp cooler has pretty much become necessary for all the beers brewed this summer. If your ambient temperature is 70° - 75°F you won't need to worry about heating to maintain the temperature.
I've never had a problem dry hopping in the primary. Should say the largest dry hop I have used is only one ounce of hop pellets. I do use a catch bag on the end of the siphon tube in case some hop particles make it through. Picture of gadget here in post #11.
Second image won't show but is in post #11.