The 0030 is their soft firmness, while 0020 is their extra soft and usually only available on penetrables, and packers unless you ticket and put in a special request. Medium firmness is 0050 and does well with most toys, for most people. Now, whether or not a medium firm will be too difficult for you to use comfortably on L/XL toys is totally up to your body. These toys can be a pretty steep learning curve sometimes; one person may love XL's in medium, larges in firm, but someone else may be like "Oh, no way! Ow!" The larger/firmer the toy, the more difficult it can be (for some) to use. It makes them feel larger somehow, the firmer firmness. Way back, when I got my first larger toys, a medium Crackers in medium firmness, I found it horribly painful. I couldn't get it in for the life of me. Reordered it in soft and now it's much easier. My large Nox in soft still feels too large to take comfortably at times, and I doubt I'd be able to use my medium Flint if he were in anything other than extra-soft.
Now, some toys in larger sizes, really don't do well in soft, like the longer/thinner toys due to them being unable to stand up properly. Toys like Chance get really floppy in soft and make insertion a nightmare. That's been my experience.
The rule of thumb for many seems to be going soft firmness on larger toys, purely for comfort's sake. I agree with that. Many of BD's larger smalls and mediums I also get in soft firmness. They are just too uncomfortable (for me) any other way.
