English Comp w/essay is graded by College Board (the owners of CLEP).
Freshman Comp w/essay is graded by your school (TESC).

I'd imagine you have to be enrolled at TESC in order to get it graded by them, so you should just go with English Comp w/essay if you want to hold off on enrolling.

As far as taking both, you cannot get credit for both. TESC considers both exams to be worth the same classes. This makes the test duplicative. Taking both will not do anything because you can only get credit for English 101 & 102 once.

This does mean that if you fail one test, you do not have to wait 6 months for another shot at the credit. Just take the other test.

__________________
CLEP exams passed:
Management, Accounting, Marketing, Macroeconomics, Microeconomics

DSST exams passed:
Human Resources Management, Organizational Behavior, Statistics, Management Information Systems

Earned:
B.A. in Business Administration: Technology Management (magna cum laude) from Saint Leo University

In Progress:
M.S. in Leadership: Business Ethics from Duquesne University (27 credits completed)