Link to Softr Specific Fillout Guide
I’ve been using fillout for a while and had not realized they created this guide. It gives beginner friendly directions on passing different values into the form, including code snippets for embedded forms 
Sharing in case anyone else finds useful!
For embeds, their support agent provided this screenshot to demonstrate what URL parameter language can be modified in order to use their URL parameter feature you configure in the settings for your form
