I'm no electrical or sound engineer but consider:
This visual comparison to Denefrips DDC clocks is interesting. https://www.youtube.com/watch?v=3SbK2kxg7X0
Alvin calls both Hermes and Gia clocks Oven Controlled, though I wonder if the Hermes at half the size are actually Temp controlled. As a lexicon aside, all the Denifrips clocks are FEMTO clocks, precision crystal, TXCO, or OCXO.
USB, SPDIF, COAX, and the Ethernet are usually Asynchronous protocols with embedded multi-clock streaming (sorry Hans)...a DAC connected via these uses the embedded source clock in the signal at first... but the Denifrips DACs use a FPGA chip to buffer and re-clock (using the Source(sync) or DAC(async) clock) all incoming signals before R2R digital conversion...including I2s, which is Synchronous (with 2 clock channels, word and global, and the data channel). With a synchronous connection the Source clock is used...the "source" may be the Digital transport, Streamer, or DDC.
My ears clearly prefer the I2s sound (lower noise floor) from OPPO 83-HDMI breakout box-Pontus II 12th-Holo Bliss KTE-Susvara HPs, though I believe it's the OPPO clock being used. Also USB is not far behind. Probably a Hermes in the chain would clock and sound better.