Hello Brikou, thanks for your question (and nice game).
About warnings, it seems you are trying the git version of liblcf and Player, which added multiple sanity checks. In case these skill IDs in your database skills tab are probably invalid because the database had some skills and later removed but the actor still has references to them (otherwise there is a bug), a workaround to “silence” them is by removing (if possible) these references to skills able to be learnt in the database editor. This is however a possible easy fix from our part.
On the lag issue, the current web Player implementation loads assets on the fly (using asynchoronous XMLHttpRequest), this was intended to load the game as fast as possible, but indeed this makes the game wait for some assets and display pictures or play music later than expected or desired. A possible workaround is edit the game and preload files by loading images off-screen and music and effects which are important to be on sync and stop them immediately. This might be improved in the future, but needs improvements to the liblcf library first. It is recommended to preload just the really new files needed each map and just for critical ones to make gamers get a better experience without waiting too much. Assets get cached by the browser, so this is needed just once for the whole game.
Concerning the skipping title scene feature, EasyRPG Player has in the roadmap adding AEP (Auto-Enter Patch) support, but in the meanwhile you may add the parameter
new-game to the URL. Demonstration: https://brikoumaker.github.io/LAQUESTION/La%20Question/?new-game
Update: I’ve seen certain lag while loading sounds (maybe due to libsndfile), I’d recommend to convert them to Vorbis format because they are a lot smaller (and maybe Opus, but not sure if current web Player has Opus format support enabled).