It should be the exact same site, but http is less secure than https (meaning it's easier for someone to intercept the connection and modify what gets sent back to you)
It's sounding like you had jar files assigned to a zip manager that just auto-extracted the installer
No I remember now, Windows tries to be smart and and Explorer has a zip browser built in, it wasn't a folder Windows just seamlessly switched from files to zip-file contents
In the context of 1.13 or later this appears to be the count of mods in a single jar as indicated by the jar's mods.toml (only if it's more than one).
In the context of older versions I don't know and don't care to look it up
On CurseForge a server pack is just an additional file containing the mods and config folders (and their contents), and with the more advanced packs a script to auto-install Forge against our wishes