Confirmed Info
General
-Inspired by Pokemon Yellow
-Setting sees players returning to Kanto Region
-Pokemon Go is not required
-Transfer Pokemon from Go into Let's Go (one way xfer). Early info indicates Pokemon moved from Go to Let's Go will appear in the Go Park where players must capture them again in Let's Go P/E.
-Version differences: In addition to determining your first partner Pokémon, there will be some differences in the species of Pokémon that you encounter and the rate at which you encounter them based on whether you choose Pokémon: Lets Go, Pikachu! or Pokémon: Lets Go, Eevee!
-Follow Pokemon return
-Local Coop By sharing one of the Joy-Con controllers with a partner, two players can adventure at the same time. Throw Poké Balls together when you encounter Pokémon to boost your chances of successfully catching them, or have a friend lend a hand by joining you in battles against Trainers in your game.
-Your starter Pikachu or Eevee cannot evolve in the Let's Go games.
-Masuda confirmed that first 150 Pokemon as well as their Alolan forms from Sun and Moon
-There is no Pokemon breeding (and therefore no eggs) in Let's Go Pikachu and Let's Go Eevee.
-Masuda confirmed that you will be able to trade Pokemon between the Let's Go games.
-You can connect with other people in Let's Go Pikachu and Let's Go Eevee via both local wireless and Wi-Fi, Masuda confirmed. Though you can battle online, there are no ranked battles in the Let's Go games.
-Customization options shown in trailer for dressing Pikachu/Eevee
Pokeball Plus
-Pokeball shaped Joycon
-Control stick and button on top, LED lights around middle, vibration function
-Compatible only with Pokemon Go and LGPE
-3 hr battery life
-$40-45
-Can be used as a Pokemon Go Pro accessory
Wild Pokemon Encounters
-No wild pokemon battles
-Wild Pokemon appear in overworld, walk up to them to initiate catch sequence
-Use of Go Capture Mechanics
-Masuda did mention during our Q&A session that the Let's Go games are like any other main Pokemon RPGs in that they're both "accessible" but with "depth" for those who want it
-Trailer Shows Wild Pokemon with Level(from old games) and CP(from Pokemon Go)
Trainer Battles
-Seems to retain older RPG battle system
-XP gain from catching Pokemon and defeating trainers, though Masuda said the leveling system hasn't been finalized yet
-Trailer shows only level not CP in trainer battles