Hey man, don't worry, clearing things up and helping people is my job, so let's dive in.
You can have maps in the standard RPG Maker style (with all their usual mechanics) as well as Metroidvania-style maps; there’s a specific tag the plugin uses to identify a map as a Metroidvania level and make it behave accordingly. Maps generated by this editor come with that tag and all other necessary settings,built right in.
(However, I haven't tested this plugin alongside others. It was designed specifically to create Metroidvania-style games, so I can't guarantee compatibility. Its architecture makes deep changes to the RPG Maker engine and adds elements like gravity, screen effects, and map/time flow, so it's worth checking if your existing plugin suite relies on those same elements to function.)
You can use custom sprites or assets from the RPG Maker RTP (MZ, MV, XP, etc.). In the example video, I used only standard RPG Maker sprites, but your game's visual quality will depend on the sprites you choose. If you want the fluidity and effects typical of this genre, it's important to use custom sprites, especially for actions that don't exist in standard RPG Maker, like jumping, sliding, and dashing.
The same applies to enemies.
Personally, I think relying solely on standard RPG Maker sprites for this system is quite limiting. To unlock the tool's full potential, ideally, you'd create sprites for every animation pattern and mechanic in your game. That said, everything works fine as-is; the editor also includes a pixel-art-based attack effect creator featuring motion animation and a particle system.
Ultimately, sprites aren't what determine how fun your game is. However, I’d personally recommend having played a fair number of Metroidvanias first so you understand the genre's mechanics and aren't caught off guard by the configuration requirements; using this plugin effectively demands some knowledge of game design, as well as how frames and particles work. I hope I’ve answered your questions; just let me know if you have any others.