I do 4 L batches in 2-gal food-grade buckets.
Go metric, buy a scale, and do everything by mass. At room temperature, 1 L water = 1 kg (within ~3 g at least).
At that size, even a cheap induction cooker can hold a vigorous boil. If I were still brewing in the house, I'd do the mash-in-the-oven trick, I've relocated my brewing to the shed; so i have to do the best I can with reflectex insulation to hold the mash temp.
I use 2-gal food-grade buckets for primary, but you can also get 1-gal mason jars or repurpose the 1-gallon "carboys" that Publix sells their organic apple juice in. Smaller thermal mass makes it easier to keep fermentation temps down -- there just isn't enough mass there to get much above room temp.