As stated on your other thread, 96wt is fine for that tank if your considering a BTA. Be prepared to change the bulb twice a year.
With your two Clarks, you'll want at least a fully open 4-6" BTA to start. Any smaller and they might be a bit rough on the anemone.
Long term, your clowns can outgrow a 20H as well. 4-5" is not unusal for healthy Clarks.