There's a space between "casual" and "hardcore" that isn't well represented in the OP.
I'd define "hardcore" as essentially playing or running at a frequency of at least once weekly. Doesn't matter if the weekly participation is spread across one, two, or more groups/campaigns; if life circumstances allow you to play every single week--- and the principal "others" in your life have given you the go-ahead to do so---that's what I'd call "hardcore."
I hear folks on these boards talk about, "Well I'm running my Thursday game then playing in my Sunday afternoon group game," or "I'm running a casual/drop-in at the FLGS on Saturdays, then running my online group Wednesday nights" and just stare in awe and envy at the amount of time available to them.
Even so much as, "We have a weekly group of 5+ members that runs without fail as long as at least 3 people are available (GM + 2 players). We have a standing rule about how to handle your character if you're absent, and we fully expect to hold a session 47 out of 52 weeks a year (all weeks other than Christmas, Thanksgiving, July 4, the one week in June when the GM is on vacation, and the week of GenCon)" feels pretty "hardcore."
For the "hardcore" it's a given that significant chunks of discretionary budget are allocated to support their chosen hobby.
Below "hardcore" status is generic "active" status.
"Active" = participating (playing/GM-ing) in an online or in-person campaign at least once monthly but less than weekly, and contribute some amount of $$ annually to support their participation in the hobby.
"Casuals" are a small step down, or even a subset of "Active." I've seen "casual" players that will happily participate in a once-or-twice a month group, but it's more their mindset or level of investment that differentiates them rather than frequency of play. These are folks that are happy to show up if it isn't inconvenient, but spend nothing or next to nothing on the game or books, and often don't even have their own dice.
Rather than "Fringe," I'd call those who continue to take an active interest in the hobby, including spending money and time to maintain a connection to it even when not actively playing, as "Observers." (Frankly, if you're an RPG company, these are the absolute best customers. They spend money, but are highly unlikely to be vocal dissenters or detractors of your product, since they're not actively using it in "real game" situations.)
"Inactives" are those that have completely fallen out of the hobby. No active participation. Do not participate or spend money on the hobby.
In my experience, the widest "cultural divide" in the hobby is between the hardcore and literally everyone else. The amount of energy, time, money, and attitude committed to the hobby by the "hardcore" is much higher than even the "active" group. For the hardcore, roleplaying is truly a lifestyle, and not just "one of many enjoyable pastimes."
