I really want to design options namely background, font, icon and border. In particular, I need to create customer form with customizable form appearance and especially with responsive bootstrap framework. Could you recommend me a suitable extension to support me to do that? Thank you in advance!
Try this Custom form for Magento 2. The extension has flexible features for creating forms with different input types. What is more, the module creates responsible forms which provide seamless user experience in all devices.
Hope that helps!
I believe Form Builder will be a solid choice for your requirements. It's packed with Bootstrap 3.x to bring you 100% responsiveness. Also, design options for fonts, icons, borders, and background are available. Especially, with visual form creator and Drag 'n Drop feature supported, it will be a powerful supporter. You are also prepared with 14 ready-made templates if you prefer a quick way to build form. Hope this help.
Also take a look at Magento 2 Professional Form Builder extension to be able to:
(a) Create multipage forms;
(b) Edit attributes, styles, events per element;
(c) Filter forms on admin grid;
(d) Create copy or backup of forms on admin grid;
(e) Collect data in the database and manage it in backend;
and much more.