Hi! The most of the stuff is modular, but the PSX Mega Pack II for instance also contains whole structures and buildings. You can use the showcase pictures as reference to put together the levels if you like. The PSX Mega Pack II also contains a building example made from the modular bits.
Okay! They're the same style and made to suitable to be combined with all my PSX series packs, so they might look similar because of it. If you're looking for the best value, I'd recommend the PSX Mega Pack II, as it's the biggest and the most recent pack I've made. It has 2.5-3 times more assets in it :)