As in my previous post the different settings are mostly preference. However for relic hunting the most important thing to do is make sure your running in iron mask and not a disc pattern, prefereably as low an iron mask setting as you can..
Me I always hunt -15, it knocks out the majority of bad iron yet lets most reachable targets come through in that same iron.. You will get more iron falses but after a while tehy are easy to tell from good targets in iron.
My choice is ferrous audio because it allows low conductive targets to come through wth a higher tone, while most iron hits will be low toned.
Set your sensitivity to as high a setting as you can and remain stable, threshold will go away with too high a sens setting as well as from anything disced out, so by keepig a low iron mask setting you will be able to tell if its iron or too high sens thats causing nulls.
Another thing to remember is, the more nulling the slower you should sweep and thats true whether the nulling is from the grund, disced tagets or even too high of a sensitivity setting.
With a solid threshold in good ground you can sweep quite fast as long as you stop and check out each target you hear, you will get more falsing with a faster sweep though..
My prefernce in the recovery mode is fast, but my sites are quite iron infested, as are most of the better relic sites.. Others have varying opinions on where you should set your recovery speed.. Try them all to see wich you prefer and gives you the best performance.
I dont use too high of a gan setting usually around 6 or 7, use more if you hearing is bad or your trying to get deeper, but be aware a higher gain makes falses sound lots better.
I use normal audio because its faster and gives a distinct round sound on good targets, but again its a matter of preference.
I get deep with the fastest settings, so am unconcerned whether I am in the deepest mode, because the biggest factor on how deep you can get in any area is the amount of trash or the amount of mineralization in that ground. I dug my deepest land coin a large cent at least 14 inches and a seated in dime at 11 in good ground with my fastest settings...
I dont thing trying to get a deeper setting gonna get me many more targets.. I havent found too many sites with good targets at depths a deeper setting change would help. Either the targets are out of range of any setting completely, or something in the ground is hiding them no matter what setting ou use.
Get used to the settings you prefer, and you will not be missing much for others to get.. Learn how the targets react and sound with those setings and you will be suprised at how good you get at telling good from bad targets no matter where they read on the screen. Even good iron sounds good if you have it set to pick it up anyway