You get everything in it and the future updates, it's a one time payment. If you find some description confusing, please let me know, and I'll try to make it to communicate better! :)
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 :)