Unless you are going to start downloading 24/96 files then why do you need it?
USB is fine. I have tried my Beresford TC-7520 with laptop (USB/iTunes) and iMac (both USB and optical with iTunes)
There is no difference so long as you have optimised the laptop or Mac settings accordingly to the correct sampling rate and word length.
Yes Macs need optimising in 'Audio Midi Setup' (and iTunes) or they sound dire. Don't believe the Mac hype that they sound great 'out of the box'. Leaving upsampling - or downsampling - to the Mac's own software is disastrous! Set it yourself in 'Audio Midi Setup' (according to whether you are using 16/44 or 24/96) and let the DAC upsample - if your DAC has that feature - like the DacMagic for instance. (Remember iTunes is always 16bit 44.1 khz on a Mac or PC)
On a PC/laptop you need to set the max wordlength and correct sampling rate in Quicktime preferences (for iTunes) and turn system sounds off in Windows.
If you are going to play a mixture of 24/96 and 16/44 stuff then you are going to need to optically connect whatever DAC you are using and don't use iTunes for the 24/96 files. It will import them fine (WMA not FLAC) but automatically convert to ALAC in 16/44 format.)
Go to the Benchmark Media Wiki and have a good read of the relevant sections (especially the bits about leaving all the volumes in system and playback software at maximum or 'Unity gain' for the posh phrase
)
It explains it all very well for setting up PC or Mac or Windows Media or iTunes etc. (And a lot of other stuff I am too lazy too type here.)