[KAMiKAZOW]

The CPU thing is either a bug or file indexing is not yet complete (although that should not take more than a few hours).

How much RAM is utilized depends on the components you loaded. "Convenience distros" tend to start more services by default. The KDE Workspace is very modular. You can disable/remove many things, esp. if you compile yourself. That said, it's not a workspace primarily for low-end computers. If it requires more RAM than your PC has, maybe look at LXQt.