I have a long history of mostly paranoid delusions (thought broadcasting, people going through my trash to steal my ideas, government stealing my hair from the barber shop, space aliens coming for me in my sleep, etc.). The only time I can remember having a grandiose delusion is when I thought I could predict the future and would stay up nights writing my predictions down. I seriously thought I would be the next Nostradamus, lol. So, no, they don't have to be grandiose.