Since the beginners guide should answer a lot of your questions, I'm just going to cherry pick a few.

5) The Intercontinental championship matters a lot because it was basically Shinsuke Nakamura's personal title for several years and he was a top guy in NJPW before signing with WWE earlier this year. IC title matches have main evented many big shows, including the Tokyo Dome. It's absolutely not seen as a joke.

6) The Junior heavyweights are distinctly midcarders in NJPW. The Heavyweight title is way more important than the Junior title.

7) The Heavyweight Tag titles mean more but really neither mean much these days. Both tag divisions are a glaring weakness in NJPW's current booking.

9) NJPW's booking in general was a shit show in early-to-mid 2000s. Long story short NJPW founder Antonio Inoki had a huge boner for MMA, gave big pushes to mostly low level fighters, had wrestlers do MMA fights (guess how that worked out) and damn near killed the company. Fujita, Yasuda and Sapp are the guys who stick out like sore thumbs.

10) Before they introduced the IC and NEVER titles, Heavyweight title reigns and G1 wins were the two big ways to measure success for heavyweights. These days the winner gets a Heavyweight title show at NJPW's biggest show of the year, hence the comparison to the Royal Rumble.

11) Best of the Super Juniors is an annual round robin tournament. Super J Cup is an occasionally held interpromotional single elimination tournament.

12) They are doing a Super J Cup this year. The first round was a few weeks ago and the rest of the tournament is happened later this month. It's always possible those other tournaments come back but they haven't done them in years.

13) Gimmick matches in general are rare in NJPW.

14) Occasionally he'll get booed but nothing compared to John Cena's reaction for years.