Most (not quite all but close) competitors find better accuracy with Swiss and greater (not not perfect) consistency from lot to lot. Out in your neck of the woods (Byers CO) last weekend, the biggest match of the single-shot cartridge, long-range matches concluded. I doubt more than a few used anything but Swiss, and I would wager that exactly zero of the top ten used anything but Swiss. The equipment report should be out shortly. Probably by the end of the week.
Generally, Swiss 1.5 fg is considered closest to C&H #6, but there is really no absolute measure that is appropriate for that comparison. OE can be fast, really fast, but some batches are not. Swiss tends to be fast, but OE can be faster (or slower). Faster is not to be conflated with better, of course.
Paper patching for competition and hunting is my gig so to speak. I do it a lot at both levels and in many different formats including levers, single-shot cartridge rifles and muzzleloaders over the last 25 yrs or so. But I have not done cartridge doubles, yet.
You will probably spend some time in the black magic of lubes and the nuances of compression, grease cookies, bullet taper, paper thickness and composition, etc. This why I was and still am so interested in some details in the thread on "Dis-assembling antique collectible cartridge".