I meant to say that you can "increase the gain and lower the threshold". The threshold is smoother in Relic normal position allowing a lower setting whereas the same setting in C/J is quite chattery. A lower disc helps avoid 'rejecting' targets and can increase depth but is not related to this subject.
A lower frequency of about 3khz to 6khz would be more effective for coins.
A higher frequency of about 50khz to 60khz would be more effective for tiny targets such as gold flakes and very small foil targets.
The differences you are noticing are caused by something other than the frequency. This still does not explain why you are able to detect small jewelry at greater depth than in the relic mode. Once you are proficient with Relic mode, you can sometimes get more depth than when using C/J mode. Also, the name of the mode is not always the best mode for the indicated hunting style. Sometimes Relic mode is better for certain coin hunting styles and Prospecting Mode is better for some relic hunting styles, ect.
I still think the difference in SAT speed is causing the biggest difference between the two modes.