Hi,
To answer your questions.
1.In this case I didn't extend from any table. Task table is pretty normal to extend from. Just remember that extending a table or creating a new may result in that you need Platform runtime licences. So talk to you SN representative to be sure.
About when to do it, read this post here which gives an excellent overview: When to Create a New Table vs. When to Extend
2. You fetch the data with server script and then put it into "data" for the client script to handle.
3. If you want to have data from your instance, you need a server script.
recordWatch is used to dynamically update your widget with data if for example a new record is created/updated in the table.
Take a look here, this short demo also shows how to read from data from a table.
Real Time To Do App using Service Portal & Record Watchers - ServicePortal.io - Service Portal, CMS,...
Let me know if you got more questions.
//Göran
