Best digital format (non streaming)

Assuming context of a high-quality studio master.

It depends on genres of music you are listening to.

For "simple" music, e.g. "a girl and an acoustic guitar", majority of pop songs, 16/44.1 CD format is more than sufficient.

To cover "complex", e.g. prog rock, classical, PCM 24/192 or DSD128 would be better.

For "extreme", such as symphonies requiring 120+ players, PCM 32/384 or DSD256 may be called for.

For storage efficiency, losslessly compress with FLAC or ALAC.

DSF over FLAC, never proprietary ALAC.

Think of a multi-lane motorway/freeway. The number of lanes would represent the bandwidth, and the cars going along the road would be the data, so too many cars and not enough lanes=problem. 

+1 @drmuso and @kr4 

A great multichannel mix can add so much to Symphonic recordings, and in two channel a DAC that can accept the DSD output is also special

For now, I will tray give multichannel a first try, using a Sony X700 via HDMI to my Onkyo. I do NOT know what the signal format will be with this combination, but found it the only way (bought 2 SACD 'capable' players initially only to learn that they don't play true multichannel SACD only read the CD side) using HDMI with a Sony player. Not sure if receiver supports DSD, or if it will be LPCM or PCM. Receiver is Onkyo TX-RX810: 

Processing Features

• HDMI support for 4K/60 Hz, 3D, ARC, Deep Color, x.v.Color, Lip Sync, Dolby Atmos, Dolby TrueHD, DTS:X (with future firmware update), DTS-HD Master Audio, DVD-Audio, SACD, multichannel PCM, and CEC
• HDCP 2.2 supported on HDMI inputs 1-3, main out, and sub out
• Dolby TrueHD and DTS-HD Master Audio decoding
• AK4458 384 kHz/32-bit DAC (8 channels x 1)
• 32-bit digital signal processing engines
• Four DSP gaming modes: Rock, Sports, Action, and RPG
• Theater-dimensional virtual surround function
• Direct Mode and PureAudio Mode

• Atmos, TrueHD, Dolby Digital Plus DAC: AK4458 384 kHz/32-bit

  DTS-HD Master Audio DTS:X via future firmware update