If you're going to go for the square-style tarts, either method will work. In both cases, dock the centres of the tarts (where the pears will go) with a fork to stop them rising as much. The way i'd be tempted to do it would be in a tatin-style, using a tartlet baking tin. If you cut the cheeks of a peeled pear, each cheek should fit perfectly into a normal sized tartlet tray. Just pop a small knob of unsalted butter into each space in the tray, a teaspoon of soft brown sugar, and then the pear (flat side up). Cut circles from your rolled puff pastry slightly larger than the size of your tartlet moulds, and place one over each pear, gently tucking the overlapping edge down the side of each pear. Eggwash, and place in a hot oven (about 200 C) until risen and golden brown. When you turn them out, the pear should be coated in a lovely brown caramel, and sat atop a light, crispy puff pastry.