-Why do I have to subscribe to all of these mods? Won't it be really confusing to enable the right things?

No, it won't. The beauty of this modpack structure is that it automatically enables and stacks the mods beneath it. After you've subscribed to all of the included mods, you will only need to enable this modpack with a single click to set up all the mods it depends upon. It's really, really easy.

On a philosophical note, this method also distributes credit to all the hard-working modders upon whose work this modpack depends. They have their mods up on Steam and you should subscribe to them, not just access their work through an independent modpack.

-Can I reuse parts of this modpack?