I2s is another transmission method, an alternative to USB, SPDIF(AES & RCA COAX) or even TOSLINK.
Currently I2s is usually transmitted using HDMI or RJ45 cables.
PCM is a method of storing music and usually uses WAV or FLAC formats.
DSD is the King of the Hill and is usually stored in DFF files, unless DSD is on a SACD.
If your DAC cannot play DSD it will be converted to DOP, not quite as good but acceptable.
There are also Apple formats, MQA and MP3.
I don't know of any format or currently used frequency that I2s cannot transmit.