-
-
SurveyJS
Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.
Personally I try to keep it simple. I don't like to burden myself with X file types across X device sizes. I usually go for creating a single image version that's large resolution (Often ~ 2x what's really needed in terms of viewport pixel dimensions) then use JPG with a manually adjusted quality setting to bring the size down or PNG ran through tinypng. Alternatively Sqoosh is great for playing about with settings. I usually aim for about ~300kb or large/hero images and 50-150kb for in-content images.