Here's a good summary with info from all the previews via
Shinobi602 on Twitter:
Press got to play a whopping 30 hours of the game, that is around 40% of the story says Kojima
"Tighter, pacier, more dynamic, more gripping" than the first game
4 difficulty settings: Story, Casual, Normal, and Brutal
Played on base PS5, "impressive photorealistic graphics" that draw you in right away, "hugely increased" level of detail
"Fantastically surreal" bossfights
Takes place 11 months after the first game with Sam living with his daughter Lou in a remote area in Mexico
After connecting America to the chiral network, deliveries are now automated by AI
His peaceful life is disrupted by the return of Fragile, now running the company Drawbridge, who sends Sam on a mission to connect Mexico to the network and then to Australia
Pacing is improved over the first game, swiftly gets players into gameplay
Corpus: In-game glossary similar to Final Fantasy 16 that can be opened at any time, including mid-cutscene, to recap and explain plot points, characters, places etc
Expanding gameplay systems was a major focus, world feels more dynamic and diverse with more opportunities for player expression
Still focused on taking cross-country delivery jobs through hostile landscapes, but much more evolved like going from MGS1 to MGS2
More streamlined menus, clear info on your objective, equipment, routes, less frustration in traversal
Combat now plays a greater role, Kojima added more options because so many people all over the world were asking him to make another Metal Gear
Sam now has to also contend with extreme weather conditions. Sandstorms can topple you over, intense rain leads to floods, earthquakes shake the ground, avalanches can come crashing down
Tons of environmental diversity, barren mountains, white sandy deserts, lush jungles, cities, etc makes the first feel static by comparison
Time of day (sunlight, nighttime) can impact the temperature of your precious cargo
Asynchronous online connectivity expanded with more structures like ziplines that now curve, safe houses for checkpoints, ramps that can shoot Sam across the air like Sonic
You can level up your abilities through use, like stamina, proficiency with weapons, skill tree buffs like better stealth that gives improved noise cancellation and enemy alerts. Likewise more time in combat unlocks better ammo, scanner range, etc
You can customize your backpack with lots of attachments like extra ammo pouches, shields, and more
You can also customize vehicles like adding an arm to a truck that will automatically grab lost packages, machine guns to auto shoot enemies
Lots of new options to encourage experimenting your approach, like finding extra tools like powerful gloves that let you punch mechs in the face or an otter hat to float in water
"Significant" number of side quests with meaningful rewards: special weapon schematics, narrative payoffs, skill points to unlock footstep dampeners, aim assistance, vehicle recharger, etc
Combat is vastly expanded and improved, in many ways "feels like Metal Gear Solid 6"
Mexico and Australia are filled with enemy bases to infiltrate, ripe for silent takedowns or gunfights that feel "punchy"
There are new human enemy forces such as bandits and armed survivalists
You can wear different camo types to blend in and throw out small puppet "Dollman" into the air to scout out enemies
You can now put down Sam's backpack to allow for more agile movement
Lots of weapon options from pistols to assault rifles, shotguns, sniper rifles, grenade launchers, 'blood boomerang', the rope-firing Bola Gun, and more
Battles against BTs are much more engaging, with new enemy types that can also physically see Sam, not just sense him
You can unlock a music player in the game that lets you play a playlist of tracks you collect at your choosing
.... Thats all? 
