Oh and also what SuperGMs play it.
Learning Sicilian

yeah 6... e6 and 6... e5 are both appealing in the Bg5 line. I'm going to look at a bunch of games and see which has better results. and which suits me better.
Possibly of interest:
Starting Out: The Sicilian, 2nd Edition
https://web.archive.org/web/20140627122350/http://www.chesscafe.com/text/hansen123.pdf
Anti-Sicilians: Move by Move
https://www.everymanchess.com/downloadable/download/sample/sample_id/119/
Sveshnikov vs. the Anti-Sicilians
https://www.newinchess.com/media/wysiwyg/product_pdf/9003.pdf
http://www.jeremysilman.com/shop/pc/Sveshnikov-vs-The-Anti-Sicilians-76p3890.htm
Grandmaster Repertoire 6A - Beating the Anti-Sicilians by Vassilios Kotronias
http://www.qualitychess.co.uk/ebooks/BeatingtheAnti-Sicilians-excerpt.pdf

Possibly of interest:
Starting Out: The Sicilian, 2nd Edition
https://web.archive.org/web/20140627122350/http://www.chesscafe.com/text/hansen123.pdf
Anti-Sicilians: Move by Move
Sveshnikov vs. the Anti-Sicilians
https://www.newinchess.com/media/wysiwyg/product_pdf/9003.pdf
http://www.jeremysilman.com/shop/pc/Sveshnikov-vs-The-Anti-Sicilians-76p3890.htm
Grandmaster Repertoire 6A - Beating the Anti-Sicilians by Vassilios Kotronias
http://www.qualitychess.co.uk/ebooks/BeatingtheAnti-Sicilians-excerpt.pdf
thanks

Considering you play the najdorf you will probably want to adapt piece setups similar to what the najdorf provides.
Against c3 lines both 2.d5 and 2.nf6 are good. Neither really involve a najdorf approach but both are considered widely to be the best moves so pick one of those I guess.
For the smith morra(2.d4) I recommend accepting both pawns and than playing nc6, d6, nf6, and a6. You should be fine at that point.
I don’t know anything about 2.f4 so I can’t really help you there, but it’s similar to the Grand Prix so I think just play nc6 ,g6,d6,bg7
Against bg5 najdorf e6 is the main line, but I actually recommend nbd7. MVL has been playing it a bit recently and it scores better
Against be2 and be3 I recommend you play e5, be6, be7, nbd7, b5 in some order and you have a fine position.
Against h3 both e5 and e6 are fine
And against f4 I believe the main line is e5
Finally, the US open is 9 rounds and you may play black 4 rounds with some opponents playing d4, and you may not even play many 2100 players, however, it’s still useful to study these lines for future references so don’t get discourage if you can’t play them this tournament.

You won't learn the Sicilian defense in 5 days. Stick to your normal openings for this tournament, especially against stronger opponents.
I will be playing in the U.S. Open (7/31 - 8/5), when my rating would probably be about 1700. I made the choice to try to play the Sicilian against 2100+ players. Can you recommend lines to play in:
1. e4 c5 2. c3
1. e4 c5 2. d4
1. e4 c5 2. f4
1. e4 c5 2. Nc3
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 then
a) 6. Bg5
b) 6. Be2
c) 6. Be3
d) 6. h3
e) 6. f4
?
___________________
Against all lines that are anti-Sicilian remember that all 2nd moves by White except 1.e4 c5 2.Nc3(closed sicilian) or 2.Nf3(standard sicilian)) are suboptimal moves. Suboptimal moves by White lead to inferior variations for White. Of course knowing those variations is an encyclopedic memory volume. Your best defense is to keep in mind the thematic squares and tactics in typical sicilian positions. The key thematic square in the Sicilian is the square d5. Other than that it would be a good idea to have the computer to build an opening tree of the Sicilian and practice with it for next years US Open.
"Generally speaking, 'Starting Out' and 'Sicilian Najdorf' are not exactly words that one envisions in the same title, because anyone who is just starting out should not dive into the vast ocean of theory that is the Najdorf. For beginners, the time invested in studying even minor lines can be more productively used solving tactical puzzles and basic endgame technique.
...
... In some lines, a good understanding of basic principles will take you far, while in others, such as the Poisoned Pawn (6 Bg5 e6 7 f4 Qb6!?), memorization is a must, as one wrong move can cost you the game in the blink of an eye. ..." - FM Carsten Hansen (2006)
https://web.archive.org/web/20140626175558/http://www.chesscafe.com/text/hansen87.pdf
I will be playing in the U.S. Open (7/31 - 8/5), when my rating would probably be about 1700. I made the choice to try to play the Sicilian against 2100+ players. Can you recommend lines to play in:
1. e4 c5 2. c3
1. e4 c5 2. d4
1. e4 c5 2. f4
1. e4 c5 2. Nc3
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 then
a) 6. Bg5
b) 6. Be2
c) 6. Be3
d) 6. h3
e) 6. f4
?