dBpoweramp has core limiting ability, don't really know what's SMP limit regarding max core count (whose interested in opposite to eliminate possible codec quality SMP degradation [known in video codecs] when I did tests. Don't wory re encoding is fast, meta data transfer sometimes knows to make bottlenecks.
IIRC - I've had dBpowerAmp ripping at 48x from CD and using all 16 logical cores of my Ryzen 7 1700X to write out to FLAC in real time i.e. it was ripping and encoding a CD in around a minute and a half.