I need to know is there any difference in performance or other features between bounded task flow with fragment and bounded task flow without fragment, and what is preferred to use.
and is there any difference in performance between jsff and jspx
A btf build with fragments can't run on it's own. A page fragment is a JSF JSP document (file extension is .jsff) that renders as content in another JSF page. A page fragment should not have more than one root component. This means that you should only have one layout container in the jsff which encapsulates all other components. Btf build of fragments are used as regions in other pages (even multiple times).
Btf build from pages run in its own pages but can't be embedded in another page.
More information can be found in the docs at http://docs.oracle.com/cd/E21764_01/web.1111/b31974/taskflows_regions.htm (jsff btf) and http://docs.oracle.com/cd/E23943_01/web.1111/b31974/taskflows.htm (page btf).