Can Twas Be Used in Scrabble?

Yes, twas is in the scrabble dictionary.

Is twas still a word?

'Twas is archaic rather than obsolete (as in 'Twas the night before Christmas) but is still current in the phrase 'Twas ever thus, and 'tis is still in use in the back-and-forth 'Tisn't! 'Tis so!

Is this word OK for scrabble?

"OK" is now OK to play in a game of Scrabble. The two-letter word is one of 300 new additions to the latest version of the Official Scrabble Players Dictionary, which Merriam-Webster released on Monday. ... Not all Scrabble players are OK with OK, however, especially at the game's highest levels.