Riot Phreak released a preview video on the launch patch. It's awesome and I recommend you watch it at: https://youtu.be/-wLj550BezE?si=3W32L-U61JsdG0Tt

If you don't have the time, I watched the whole thing and took notes of the main points. Here's the summary of what Phreak said, in the least amount of text possible.

Introduction/Philosophy (Most important part)

• Recognized modern League is more of an action game while Classic, goes back to it's strategic roots. As a result, expect your decision making and knowledge to have a bigger impact, on the outcome of a match.
• There will be no public data shared, such as win rates and other stats. The goal is to reintroduce the rpg side of the game, meaning you forge your own path/playstyle, while having less "hand holding" - you figure out what works and what doesn't through playing and testing.
• Balancing nostalgia with an actual playable game for everyone that wants classic and, have fond memories of different moments in League.
• Phreak confirmed this is a live service/permanent project, not a temporary game mode.
• Reassured they know League Classic is supposed to be and stay different from modern league.
• There are easter eggs, and many of them have not been found yet, on the PBE.
• Built on modern engine -> harder to develop, easier to sustain.
• Overall skepticism to release anything after season 3.
• Expect content (including champs) to be released fast, although no specifics were given.
• Phreak is responsible for game balance and will keep an eye out for long term power creep.
• Boundaries that will be respected are no faster cooldowns, missile speeds, cast times, travel times and no mana cost reductions.

System

• Runes mostly from season 4. Runes that were bad were buffed.
• Masteries straight up season 3 + rally and promote inclusion.
• All summoner spells.
• Minions and tower straight up season 3 + minor buff to stats.
• Jungle is from S3 but nerfed XP gain and included white camp. Need to kill the little guys in the jungle or respawn timer won’t start.
• Items up until season 3 with a few exceptions from season 4.
• Trinkets from pre-season 4 but you can’t pay gold to upgrade it**. Phreak considers the game worse with less vision**.
• Baron buff from S5 but the buff to minions is reserved to the siege cannon (resists, ad, range). Goal is to close the game out faster, but open to discussion.
• Information such as what a buff does, with values, now included in the tooltip. Info from the scoreboard can be pinged, equal to modern league.
• Gold bounties from S3, catch-up XP unclear if it was tuned or not.
• Everything else is from season 3.

Champions

• Release champions until season 3, potentially early season 4.
• Phreak didn’t clarify here if Yasuo, Lucian and Jinx will be released.
• Rest of the video is Phreak going over each individual champion and their kit. It would take too long to cover everything and might not interest you but in general:

1. If your champion has dashes/high mobility, has to be penalized somewhere else in the kit.
2. Fighters are more auto attack heavy.
3. Buffs from champs last substantially longer, when compared to modern.