Provide an option to turn on or off a help icon (question mark in a circle) next to a form field. Also, a field property that allows you to enter some help text. When a SharePoint list is used as a data source, default the help text to the associated column settings description field value and turn the help text icon on for that field. Keep the help text and column description text in sync if changes are made in either location. This will allow the form to still remain clean, while offering a way to provide expanded help text for certain fields to guide users on what to enter. There is an existing option for tip text, but that disappears when a user starts entering a value in the field. The tip text also only has so much room before it's trimmed by the form field control. This method of a help icon is already being used in the PowerApps designer. Look at the help icon next to the "Snap to Column" option for a form as an example. Thanks for considering this enhancement request!
PS (SharePoint and PowerApps should be in the spell check dictionary for this rich text editor on the powerusers.microsoft.com site 😉