Original AMA here. Recap below. Full transcript in the OP.

Accounts

• Once you've received an invite, you're in for good! Players in now can play in the Preview Patch 2, Closed Beta, and beyond.
• There will be an account reset at some point due to everyone getting tons of wild cards.
• After the account reset, any coins purchased will be reimbursed in full.
• There will be crossplay between devices - your progression follows you.
• Your friendslist in League of Legends will be used for Legends of Runeterra.

Timeline

• Preview Patch 2 will include Expeditions - draft mode.
• Closed Beta will include ranked mode, new boards, and guardians.
• The goal is to get every League of Legends Champion into Legends of Runeterra.
• New sets should come out every 4 months. (Starts at launch)
• Balance patches should be monthly.
• Adding additional cards between sets is something being looked into.

Economy

• Duplicate cards get turned into shards which can then be spent on crafting new cards.
• Top-tier decks should be accessible to everyone, even if they don't spend any money on the game.
• If top-tier decks aren't accessible enough, progression will require some adjusting and they will commit to doing so.
• They have a unique, paid currency with Legends of Runeterra because of platform restrictions and that it lets them tune it without interfering with their other games.

Cosmetics

• New gameboards will be coming next year and can be purchased with coins.
• New guardians will also be available next year and can be purchased with coins. Currently, your guardian is the Poro on the left corner of the board.
• They are open to additional ideas for cosmetics - they want players to be able to express themselves.

Systems

• A top priority is to ensure the team can make and push changes quickly and with ease.
• They want to allow you to rearrange attackers positioning - its in the backlog.
• Making many of the card draw and healing spells Burst is to keep the game running fast. It would slow down if opponents could react to them.
• They are not yet sure about what to do about a Standard format / rotating sets.
• The game is currently only supported on Windows, Android, and iOS because those are the most popular platforms.
• The newest Mac OS being able to run iOS apps in iPad mode excites the team.
• Having quests that require participation in League of Legends to earn Legends of Runeterra rewards are not off the table, but they should not feel like chores.
• Keyboard shortcuts were removed from the game due to bugs. If you want them, what keyboard shortcuts would you want?

Tone

• More factions will be added to the game, but they aren't saying which ones.
• Neutral cards, or cards without a faction, are not currently planned.
• It is important that they keep true to the overall tone of League of Legends, unlike how Hearthstone deviates from World of Warcraft.

Expeditions / Draft Mode

• Draft mode, Expeditions, will be a unique take on a limited format.
• Expeditions will be a hybrid between MTG Sealed and MTG Draft formats.
• Cards drafted will not be added to your collection, but rewards and cards can be unlocked by playing draft.

Awesome recap! Saw that 2nd question about the iron hands nerf and had to do a double take to make sure I wasn't in r/warhammercompetitive haha!