Useful resources for NAOMI & Atomiswave - TheArcadeStriker/flycast-wiki GitHub Wiki
Here you can access to other sections of the wiki that can give you a hand with several things related to playing SEGA NAOMI and Sammy Atomiswave games.
Here you can check an list of games that have VMU support, games that are confirmed with working/emulated VMU support in Flycast, and what are the features of each game, as well as how to use them. Several NAOMI games (but most if not all only in Japan region) had the feature of plugging your VMU with your own data from the console version to use it in the arcades; which is what "VMU support" is referring to in this case; and the features can vary from game to game.
Most if not all arcade games supported can have their own control scheme, and while Flycast always uses the standard Dreamcast controller mappings (as well as an option to show Arcade button names), what button mappings does each game use can really vary; which is why this page was made, as it contains an guide about what button mappings each game uses.
Some games have unlockables, which are time-released or through an password through the service menu. This page includes EEPROM files for several games to have all features unlocked without having to do extra steps; only by using the provided EEPROM save files. Other kind of extras are intended to be added in the future, like command lists, manuals and secret features.