Salestrekker has its own built in Fact find that is located under "Client profile". Every deal has it. In there you will be able to add and view personal details about borrowers, their income, expenses, assets and liabilities and other details.
User with broker tools accounts will see 'Broker Tools' button instead and in addition to Fact Find tabs will see all the broker tool tabs as well.
You can share deal on with clients using Client Portal and they will be able to edit their profile from there. All entries will be stored to fact find from your end (no web form integration or document sending).
Use document merge functionality to populate already entered Client profile information to external Fact Find document (i.e. create a Fact Find record).
Export, merge document preview:
Here is article that can help: https://support.salestrekker.com/documents-and-files/apply-document-merge-to-a-deal-manually