Today I bought the Happy Forms plugin, and I'm happy I did it. It took me a while to make that decision because I had a long research period first.
I noticed that Tracy from WishList Member also bought it, which make me think about possible integration with the plugin developed by his company, which would be fantastic.
I notice that Happy Forms often offers updates and new features, which is again a good thing. It means that developers have serious thoughts about this plugin.
One thing I would like to mention is that all users data are kept in the database on the server where you have hosted your website, meaning better security management, especially in the GDPR light.
I want to contradict those who noticed the negative reviews on wordpress.org: most of those who posted negative reviews are upset because the premium features are no longer available in the "free" version, which is normal. To develop a business, you need funding, and this can only come from the plugin users.
I am convinced that, in a short time, this plugin will have many more premium features, such as integration with Woocommerce.
I recommend buying this plugin. You will undoubtedly make the right decision!