A batch of Chinese interviews with Yu and Hiroaki Takeuchi have appeared. Going through them now with machine translation, but of course, it's liable to be inaccurate.
One interview in particular gives the most info about Shenmue III, but I've added details omitted from that interview that I found in the other articles. Here's what I've gleaned from the machine translated versions:
Yu describes the new combat as "very varied, richer, and more playable". Takeuchi-san elaborates that the goal is to create a combat system that welcomes players of different skill levels, and that a lot of consideration of design and balance went into making combat feel fun for all players. He finishes saying a lot of effort went into the combat. Yu's ambitions are to show a lifelike representation of Chinese martial arts.
Some mini-games from the original won't return, but there are new ones included that they feel are more interesting. Old mini-games confirmed to return are Lucky Hit, Excite QTE, capsule toys, and yes, forklifts.
Mini-games will hold greater impact and influence over the wider game because of better integration, and there will be surprises after playing for a while. Takeuchi-san is looking forward to player reactions on this aspect.
Yu's comments in 2017 about Shenmue III being a 70/30 split between old and new ideas has changed thanks to development advancing, and now stands at 50/50.
Side quests and the main story will have better integration, and form a better closed loop. A better translation might be able to elaborate on this, as machine translation threw up the word "branch" and might be related to Yu talking about quests that could have branching outcomes. Side quests will no longer be isolated from the main plot. This was apparently considered for the originals, but couldn't be achieved at the time.
Yu says Shenmue III is more of a hardcore game than the originals because of elements of playability and increased degree of freedom, it seems to be implied Shenmue III may take longer to complete than the originals (Yu says I & II are single week games, III is a multi-week game). Also seems to infer players can interact, or not interact, with content how they choose. Not completely clear on what this means.
Yu implies once the main story has wrapped up, there are other storylines to explore and systems to play. Sounds to go beyond just the mini-game and combat collection Shenmue II had once you cleared the game, and implies possibly being able to mop that extra content up without having to start a new save.