Most definitely! If you have a relationship status with them, there will be a condition for you to have a cut-scene or mailbox interaction with them.
The following non-marriageable Villagers will each have significant involvement in a cut-scene you can experience:
Caroline, Clint, Demetrius, Emily, Evelyn, George, Gunther, Gus, Jas, Jodi, Kent, Lewis, Linus, Pam, Pierre*, Robin, Shane, Vincent, the Dwarf, Krobus, and the Wizard.
That leaves the following NPCs as without cut-scenes or only rewarding you with mailbox rewards for their relationship:
Gil, Marlon, Marnie, Morris, Willy, Mr. Qi, and Sandy.
Note that the cut-scene with Gunther will be unlocked once you donate enough Artifacts.
*: Pierre's cut-scene at 6 hearts is fantastic.
Short answer: no according to the wiki
Long answer: Speed Gro only affects the rate at which the plant "matures" and not the rate at which it "produces crops". For most plants like pumpkins and melons, these are the same age so it doesn't matter, but since blueberries ,cranberries, etc all produce multiple times it is an important distinction.
Best Answer
Following this guide, the following crops provide the most daily profit:
Spring
Summer
Fall
Note that each dollar amount is by a per crop basis. So 10 pumpkins would bring in $169 in one day. This is also strictly based off of crops alone and the base quality of them. Higher quality items will increase the amount per day.