Congrats on the new 361. Toss a Lakerized™ muffler mod on there, turn up the juice a little, and you'll have a sweet little wood-killer.
As far as the chains go... for a 20" B/C you'll be fine with the RS (full-chisel) for cleaner wood and RM (semi-chisel) for dirtier wood. At that length bar, no real need for skip. Stihl calls their newer versions of these "RSC" and "RMC." If the chain that came on yours is a RSC3 (the #3 in the code denotes 'low kickback' as does the green tie link) RSC & RMC will be more aggressive, and are easily spotted by the yellow tie-link and yellow box label. Not necessarily more dangerous, esp. since this isn't your first time cutting... just be aware that these are a little more "grabby" on the upper front quadrant of the bar tip. I proved this to myself screwing around doing shallow bore-cuts with my 361, 16"ES-33RSC. "Hello Kickback!" Happened fast enough to startle me, even as I "knew" that's what I was fooling with.
The "Super L" has square-ground cutters... I have no real experience with it (I held a loop of it recently - it looked/felt very sharp
) so will limit my comments to A: Has a very involved learning curve to hand-file. B: Mostly a west-coast softwoods chain. It's not what I need in the oak/hickory/maple woods of NC... but if my little pines & poplars someday grew huge, and I wanted to slice them up really fast, square ground would be a good choice.
Nutshell fact: "Skip" chain has a 'blank' link in place of every other cutter link, and semi-skip has the # of blank links between normal and full-skip. Another way of saying this is that if regular chain has X cutter links, the full skip will have 50% of X and semi-skip will have 67% (approx) of X. Skip is mostly used on long(er) bars, both for chip removal, and ease/speed of resharpening.
Ripping (milling) chain is similar to round chisel, but the cutters are ground with different angles. I think this is to pull a smaller amount of wood per cut vs regular chain. It should also leave a smoother finish than regular. Bailey's has this (WP375-30RP regular and WP365-30LR narrow-kerf/low-profile) if your local shop does not.
Hope this doesn't muddy the waters too much... and make plans to attend Club 361's annual convention in Bermuda this winter.