older unhunted area ? no such place, unless detecting is not allowed, and even then guys have been sneaking into places at night as long as I can remember, and I am talking the last 30+ years, sure digging tabs blows, but you will be amazed at what all can and does fall into the tab range, heck even the foil range, gold rings will be there, or earrings, it all depends on the machine being used, I have zero knowledge of your machine, so I cannot give specifics.
All metal mode is just that, if its metal, be it a tiny piece of rust, a clad quarter, a tiny lead sinker, atleast any machine I have ever used that has a all metal mode...get ready for Beep-o-Matic lol.
Personally if you have a truly unhunted location, where people congregated..and thats the kicker, I dont care if you have a virgin 1700's homesite, if people never gathered there, you wont find much of anything, old does not mean lotsa goodies.
but if its a good location, I would run with as little disc as possible, for one it kills depth, and then there is the dreaded masking effects, if you are discriminating out nails or tabs, and there is say a merc under it you may or may not find it, in the old days odds are you would miss that merc, the more modern detectors, such as the multiple frequency detectors, can go right thru the masking effect as I myself am learning on my new minelab.
Not sure what state park that you got access to, but if its normally off-limits to others, you better get it in writing that you have permission to excavate there, just from personal experiance, what one DNR guy says, may be totally opposite of the next DNR guy that just happens along...
Well if you ever have a question about metal detecting in any fashion, just shoot me a message, been swinging a coil for more than 30 years now, so I have alot of tricks and tips in my little black book of secrets lol
Mike