Can I manage my existing Accounts, Contacts and Cases in Salesforce from the form?

Yes - you can.
Manage Salesforce objects from your form
When you have existing objects in Salesforce, like Accounts, Contacts and Cases, for example, and you want to allow fillers to manage the data in this objects - you can do so from within the FormTitan forms you create. This may sound complex or even impossible but it can actually be done by integrating your form with Salesforce. Our SF integration is bi directional, so it can allow fillers to view the data by "getting" it from Salesforce, and it can also allow them to update these objects by adding records, edit records and deleting records - all this from within the form.

Ways to manage data
You can combine the SF Get and SF push in the form to allow your filler to manage the data. You can have the fields in the form auto populated
from Salesforce - so the filler can view the data, and you can also have them push data to SF objects if they are updated by the filler.

An easier way to do this is with an SF table element. This element allows you to display and manage Salesforce data in a grid view. It can also display several levels, to manage parent-child data. For example: you can create a table with 3 levels: the first for "Account" data, the second for "Contacts" data, and the third for "Cases" data. and so the filler will be able to drill down the table from account and see the contacts belonging to it. He will also be able to drill down to the contact cases from there. 

How to Use the table element
When you drag this element onto the canvas it has default styling and data. you will need to configure the table columns, change the size and look of the table and finally set the integration. 
Learn how to use the SF Table
Watch a video about Manipulate hierarchical Salesforce data using a table control