So these details come from the newest Famitsu issue via both Shinki Mikami and the game's director, John Johanas, talking about the direction of The Evil Within 2. There's a bit of a summary of some of the key points here in Japanese, but I'm going to extend on them in English here.
There's some very interesting information here, I'm going to breakdown the bullet points.
-Development for The Evil Within 2 began in Summer of 2015.
-Instead of dictating the way to play like the original game did (and clarifying the original game sort of had a certain style you had to play in chapter by chapter, often with limited options in what you could and couldn't do), they want players to be able to play The Evil Within 2 anyway they like. They restrained forced stealth and combat sections to instead rather have multiple options in about any scenario, allowing players to choose whether to fight, sneak, flee, or use traps/the environment to kill. There will be scenarios where certain methods will certainly be much tougher to pull off, but they designed TEW2 so all options should almost always at least be possible.
-The game has three difficulty levels at the start, "Casual," "Normal," and "Nightmare." They mention that there are some severe differences between the three difficulties, anyone who wants to be challenged and aching for supplies should play Nightmare, but Mikami recommends actually to start with Casual difficulty as while it's certainly much easier it still isn't exactly a cakewalk either, and for the next point.
-The narrative was a big focus for The Evil Within 2, they don't want to reveal too much but they think The Evil Within 2 actually has an amazing story, which was never a focus for the original but they think the story in the sequel will surprise a lot of people. Especially in the second half of the game when it really begins to kick into gear. Mikami recommends Casual difficulty because he wants people to be able to experience the story even if they are somewhat new to the genre and doesn't want to frustrate gamers with blockades in difficulty if they're here to enjoy the story, and warns that with this decision to make Casual Mode more accessible they cracked down to make Nightmare Mode truly nightmarish.
-The story for TEW2 is connected to the original game, but there will be something in the sequel that gives the information needed from the original game for those who hadn't played it. They want The Evil Within 2 to have things for fans of the original, but also be accessible for people who never played the original game.
-For horror, this time around they focused on 'fear' rather than grotesqueness. The original game had a grotesque theme to fit with Ruvik's mental state, but the sequel while still having that morbidness has a much stronger root in the fears humans have, what people are afraid of in the back of their minds coming into existence.
-They mention the focus for The Evil Within 2 was not just to increase the horror aspects, the leading focus of The Evil Within 2 this time around actually was story but they want to keep most of that a surprise. They've also made various improvements to play style choice, and to accomplish this have made great improvements in the game's combat, stealth, movement, and trap areas.
-They confirm the game still has unlockables like the original game did, as well as ways to customize yourself with upgrades and skills (this retreads over some recent info you can read here, so I won't list it here).
-The game is still split into chapters, but in a much different way than the original game was. They say there's far fewer chapters but a lot more that happens in each chapter, and it sounds like most everything they've shown so far for the game is from Chapter 1. They hint that each chapter has a big 'open' hub world at the center of it and various stages to each one. They also say there won't be many loading screens in The Evil Within 2.
-The game will start the player off in a much wider stage, and the game more than the original will let players play the game at their own pace. There are various missions you can take on in each bigger area, some are main missions while others are completely optional.
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Apparently we also will certainly see more before the game's release in two months, but they've opted to keep most of it a surprise this time around but believe they've made something that will stick with people.
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UPDATE:
New interview with the French site Jeux Video.
One of the key things Mikami says in the interview is if the original The Evil Within was closer to Resident Evil 4 than RE1, The Evil Within 2 is much closer to Resident Evil 1 than RE4. He wouldn't go too full into detail here, but touched a bit on this, commenting that The Evil Within 2 features more downtime, exploration, and unlocking new areas than the previous one did, but there's more to that comparison but he wants to keep it more of a secret for now.
Some other key bits from the interview:
-They mention a big emphasis for them this time is atmosphere, they think what hook people over a longer period is good characters, atmosphere, over action set-pieces and they're exploring that in TEW.
-They mention they made the casual difficulty much easier to be more accessible to casual audiences.
-They mention The Evil With 2 is somewhere between a psychological thriller and survival-horror.
-Mikami talks about how he's open for Tango to try other things, and even other horror games since many on the team are passionate about horror and they had before TEW2 tossed around a very different sort of horror game, but they got an idea for TEW2 they all decided they had to make, and so they're going through with bringing that to reality.
-They basically confirm that they don't want The Evil Within 2 to be the last TEW game, they're planning it as a long-lasting franchise and hope to prove it's ability to be that with this game.
-Mikami actually really liked Resident Evil 7.