Not really advisable for students weak in english.

What do you normally write for an english essay for your trails & mid-terms? The time to experiment with your writing is during normal term exams. See which of the type of essays which doesn't give you many problems. Points which you can write down with a snap.

Bombastic words would certainly give you additional marks for your language.  But make sure the use of the word is correct. Try to add in idioms as well, exactly like the use of peribahasa in BM.
No harm writing more than the required words but try to make sure that your additional paragraphs and such are 100% correct.

I've seen examples of essays of which SPM students wrote. The essay had more than 1000 words in it. And the essay got a 92/100. Make your writing more interesting, so that the examiner wouldnt get bored.