As someone who had never played a Touhou game before in my life I can't speak to how "accurate" the game is or what the two harder difficulties are like, but what I can say is that if it's indicative of how a canon Touhou game feels to play then I certainly wouldn't say no to trying one for myself in future.
My only real suggestions/criticisms are things I'd already brought up in DMs; that a couple of accessability options for the main menu background/text would be nice, the visual effects used for the 2nd boss' spellcards lag the game slightly on my PC, and the English script could probably do with a once-over from a native speaker to catch the odd typo or odd wording, but outside of those extremely minor gripes it was an excellent first-time experience of the Bullet Hell genre for me.
Keep up the great work!