Any seed that is not a hybrid will grow true if it was grown in seclusion from others of it's species. With hybrid seeds it is a crap shoot. Sometimes you get the plant you want but most times you don't

Since most flower seeds are hybrids saved seed will not grow true. The size of the seed makes no difference.

Hybrid seeds have many ancestors and the flower it produces can resemble any one of them. It may also have been pollinated by another species and it could resemble the pollinator.

The only way to get a plant that you want is to buy seeds. Then you know what you are getting.

All that having been said I have found that some hybrid seed does come true. If you are willing to chance it go ahead but don't be surprised if you don't get what you want. Then again you may get something you like better. As I said it's a crap shoot.