Google Forms is a free service to create forms and surveys. It is mainly for the data collection needs like survey forms. Google Forms offers 15 different themes/colors to customize your form, add video and header image to your form. Whereas the other online form builders like Formstack provides premium features like accept payments, file upload, spam prevention, drag and drop interface, A/B testing, save & resume, webhooks and e-mail confirmation.
So, if youre looking to make professional forms with premium features to add to your forms, then you should go for other paid form builders. They also have a free trial period so you might want to try one of their paid plans according to your needs and then decide if its worth your money.