What is difference between Form viewer, Form builder, Form & Dataset brick and App studio forms

Form Builder and Form Viewer are custom apps that provide a system to create and submit forms. Builder can build and submit while Viewer is submit only from the forms built in builder. These use AppDB collections that sync to DataSets. These are considered legacy applications however and the plan is to replace them with Forms in Domo.

Forms in Domo can be used in App Studio and Workflows currently and is where we are actively developing and adding new features. These Forms write directly to DataSets.

The Form & Dataset Brick is a custom app that is meant to be an example of how you would make an app that writes to AppDB that happens to be using a simple form as the submit mechanism. It's meant to be a starting point for AppDB based apps where you can make your own customized form or other app. It can also sync to a DataSet but the current example app doesn't use DataSets. We are working on converting Bricks into templates in the Pro Code Editor which is currently in beta.

I don't believe any have phone number type validation, signature question types or style changes to the title.

Not sure exactly what you mean by sections within a single page but that may be possible.

The Brick won't have any of that without you custom coding all of it but it is all technically doable as custom apps can be coded to do most anything.

So sections by nature are intended to be separate pages. As far as customizable forms the forms themselves are not. It would have to be a custom app that is coded to display as a form. That would have to be fully custom code on your end though instead of something out of the box.