I guess it depends upon what you want or need for the final look. Burned edges look great if your stuff is supposed to look like it was rescued from a fire, but it's not the same in appearance as foxing. Foxing is the natural browning or sign of aging in paper, especially acid free paper. There is no charring in foxing.
Most people are more likely to have a teabag or coffee grounds than they are to have a blow torch. I think the torched look works great for things like "pirate's" maps and such, where the item is supposed to look like it's been through a real rough life at sea, but for things like books of spells it looks out of place.
Something I would add into your look for ancient paper would be to have deckled edges on the paper. That, along with the foxing of the edges, and maybe some minor tears, gives the paper the look of being hand made rather than the perfectly smooth and square modern cut edges. I'd also subject my pages to a bit of steam so that they warp. Between that and the other techniques you can produce some great looks.
If you want to have an easier time for the general look, try using a parchment paper to start with, you would still need to do your foxing and the rest, but the variations in color give you a good head start.
If you are going to have text (spells, lists of names, etc.) on the pages that people are supposed to see and maybe read, do some careful research on the typeface to keep it consistent with the age and origin, and also remember that people are supposed to be able to read it. There are tons of typefaces out there (I'm one of the idiots who creates them) to choose from, so consider all of your needs and choose wisely.