Unfortunately, the only design option that Airtable allows you to change is that you can toggle the size of each field between “default” size and “large” size.
The other design option you can change is if you choose to embed your form into another website. Then, you can change your embed code to use a different height or width.
Outside of those things, there’s nothing else available at the moment. You may want to send an email to support@airtable.com to ask them to provide more design options.
In the meantime, for tons more design options that you can customize in many different ways, I would highly recommend that you use Fillout’s advanced forms for Airtable, which are 100% free and which allow you to create OR UPDATE records in Airtable from a form.
Fillout offers lots of design options, and it offers multi-page forms, conditional paths for pages, accepting payments on forms, updating Airtable records from a form, creating linked records on a form, specifying the maximum number of linked records, displaying lookup fields & formulas & rollup fields on forms, and dozens of advanced Airtable-specific features that are not available in Airtable’s native forms.
Best of all, Fillout has direct, live, real-time communication with Airtable.
I gave a brief demonstration of Fillout on this Airtable podcast episode.