All parts of Professional Manuscript Format use 12 Point type. The Style of type can be any number of choices. The last thing you want is to make a Literary Manager's eyes cross with the type style you've used. It's the sort of type used by most newspapers and magazines like Time .
Italic type is very hard on the eyes when it's used for more than occasional word emphasis.
Line upon line of it is enough to make the average reader of play manuscripts chuck the whole thing in the waste basket. With nearly universal use of computers and word-processing programs today, most playwrights haven't seen a typewriter in years. Some common fonts for the job and that you can find in word processing programs . . . Palatino One of the most readable you'll find. Particularly good if you miss old-fashioned typewriters.