You are not likely to encounter TCG in the literature. These corrections amount to as much as about 1.6 millisends and are periodic with an average of zero. The dominant terms in this correction are have annual and semi-annual periods. There is a subtle relativistic distinction between coordinate time and dynamic time, which is not significant for most practical purposes. The rate difference from TDB can be important to long term measurements, so make sure you know which time is being used when comparing observations.
Some physical constants are different in coordinate time.
You are not likely to encounter TCB in the literature. It is the observed rotation of the earth with respect to the mean sun corrected for the observer's longitude with respect to the Greenwich Meridian and for the observer's small shift in longitude due to polar motion . Since the earth's rotation is not uniform, the rate of UT1 is not constant, and its offset from atomic time is continually changing in a not completely predictable way. UT1 - UTC is monitored by the International Earth Rotation Service and published weekly in IERS Bulletin A along with predictions for a number of months into the future. Note that when a leap second is added to or subtracted from UTC, the value of DUT1 is discontinuous by one second.