Kiwami 2 felt like it had more content than Kiwami did. Kiwami took me 60ish hours to 100% (with the completion list) while Kiwami 2 took me 100 hours pretty much on the dot (not counting the Majjima chapter, that took a couple of extra hours, but that's because I didn't rush it).
Kiwami 2 still has less content than 0 though, that game (0) just had a ton of content thanks to its two playable characters and plenty of side stories and mini games to clear, Kiwami 2 isn't quite up there in terms of content. But its still got quite a few mini games to clear, a fair number of side stories (76) and two rather large "another drama" styled missions to clear (Cabaret Club management and Majima Construction). Kiwami 2 also has the Enforcer missions and mini bosses that are located on the main game map - these also take a while to completely clear as there are a ton of Enforcer missions (think small linear "courses" that take place on previous set pieces and in both Kamurocho and Sotembori that task you with taking out all the enemies and one boss character - just like Streets of Rage or Final Fight). The mini bosses are easy to beat, but they require you to beat up tons of goons while exploring the game world so its in your best interest to tackle them when they unlock and then keep getting in fights after that to unlock the next one (I did this naturally, I had no idea how to spawn them, I just got into loads of fights).
I'd say Kiwami 2 felt streamlined in terms of content. There's a lot of stuff there to do, but it doesn't feel overwhelming like 5 did for example. You'll be able to easily clear it all if you just do a bit here and there in each chapter.