i like using a variation on the french seam Ive understood to be a mantuamaker's seam. ínstead of folding the seams back on themselves after doing the first row, one side is wrapped over the other and the second row of stitching is done next to the first, stitching in the ditch. it makes a more flexible seam as the fabric folds fewer times, and its easier to avoid the first raw edges from poking out through the second seam as they are on the outer edge of the seam allowance, not the inner. it can take some calculation though as both sides of the seam take up different amounts of allowance, so i usually use it on gathered skirts where there's a bit more leeway if i dont bother making the adjustments beforehand. it might be worth trying this, as it may offer some of the benefits of the french seam with a little less bulk.
I may have misread, i do that! You say the non variant lapped seam was used in Edwardian corsets, above that looks like it leaves raw edges in your felt example, indeed you say its used for non fraying fabrics like leather. How would you have it so thats not the case?
Sorry if it gives that impression, my lack of writing skills! The Edwardian goes under the lapped as the variant flat-fell is what was used extensively for just the reason you state, it leaves no raw edges. I also have a sneaking suspicion that i may have seen at leave one that appears to be a turned seam but i would have to look into that a bit more. Hope that clears it up :) xx