For a recipe like this, that uses roasted eggplant slices, that you then top with some extra stuff, does not require much additional preparation. If you do it like the recipe you link to, you can just:
- slice the eggplant 1/2-1 inch thick, place it on oiled baking sheet (you can brush the slices with some oil on top too, sprinkle with some sea salt - ifyou haven't salted them earlier - and add some finely chopped garlic if you want)
- put in the 400 F preheated oven for 10 - 15 minutes or until they start slightly change color (thicker sclicew will take a bit longer) - you definitely want to preserve the texture (as you already guess you don't want them to turn mushy, but rather a bit crispy - so a broiler is a good way to go)
- then top with the stuff from recipe and bake for another 5-10 mins
Note: The texture of the cooked eggplant also depends on the variety - many Asian varieties tend to get softer and creamy, where most European varieties stay firmer and meaty (McGee, Food&Cooking).
For my eggplant parmigiana I usually flour and panfry the eggplant with a tiny amount of olive oil until golden on both sides, top with tomato sauce and cheese and broil for 5 minutes, sprinkle with fresh parmigiano and serve.
Salting and draining/washing usually helps getting rid of some bitterness. However, I have grilled and baked eggplants for years without doing that and it never tasted bitter ... I think many modern varieties are already way less bitter than eggplants used to be decades ago. But that might also be a matter of taste. So this procedure is always optional and mostly depends on the bitterness of the variety.