Sound Forge Audio Studio and Sound Forge Audio Cleaning Lab are two completely different programs! The former is a fairly simple stereo audio recorder/editor, the latter is designed to fulfil a quite specific role, that of cleaning up and improving the quality of already-recorded audio (e.g. the reduction or removal of hiss, clicks, pops, etc.).
As to whether it is necessary to buy SFACL that is really a decision for you which very much depends upon whether you need to be able to "clean-up" any existing recording.
Thank you for your reply, it helps me understand. If I'm using SFACL to clean an LP or cassette tape, what is the highest resolution that I would be able to render to a file?