And if yes, what would be its multiple?

samplerate no, bitdepth yes (2x, "double precision")

lawp
samplerate no, bitdepth yes (2x, "double precision")

oh, so the "384kHz" of "64bit/384kHz engine" is just meaning the max. supported project sampling rate?

yes, as far as the sample rate.  The calculations are done 64 bit for the depth.  You chose that with the engine - double or nothing.  The sample rate works at your chosen rate.  Sample rate is a contentious topic - bit depth not so much.
 
@

parco

lawp
samplerate no, bitdepth yes (2x, "double precision")

oh, so the "384kHz" of "64bit/384kHz engine" is just meaning the max. supported project sampling rate?

Yes. Also- regarding Bit Rate, your settings for Audio Files under Preferences determines the bit depth of various things- recorded files, imported files, and rendered files, etc. So if you record at 24-bit and have your rendering settings set to 32-bit then Sonar will render to 32-bit for the files themselves. If the double-precision option is selected then Sonar ups the rate to 64-bit when summing audio from multiple tracks, etc.

Peace,

Tunes