At 3000 watts it should work well on 5 gallon batches.
I'm not sure if the dial control is on a thermostat, or just variable power.
I would use it in a manual fashion, heat strike to temp, remove heat stick and mash in. Insulate kettle for rest, remove bag and boil with heat stick.
The heat stick could also be utilized to stir the mash if add. Heat is required.
Not sure how you would use this if you wanted to automate the heat? Fwiw I have an electric turkey fryer with a similar submerged element that fits adjacent and under the basket.