Setting the Default find/replace behavior to either Fast Search, General Search, or Start of field search makes no difference to the search behavior in a form search box at the bottom of the access form where the Record Selector/Filter/Search boxes are located.
Fast search should be: Searches the current field and matches the whole field to the search string.
The actual behavoir for default setting Fast search is: General search: Searches all fields and matches any part of a field.
I put the cursor on the field I want to search but as I continue to type the search string the matches jump to different fields on different records.
Tried this with Northwind database, Supplier Details form with default setting of Fast search. I did close and reopen the database after setting options.