Vegas Pro doesn’t automatically setup a link to Sound Forge. You need to do that manually, as you could have 16 versions of Sound Forge installed and how will Vegas know which one to use?
SpectralLayers Pro is very different from Sound Forge. It operates on spectrums instead of waveforms. It was also sold to Steinberg so take my advice, consider it an obsolete program if you’re not already a user.
Just because a program is bundled does not mean it is valuable. 😉