In general you should avoid tournaments where you have opponents who are rated 400+ points above or below you.
Games between you and such opponents will not be beneficial for your learning as they will (usually) be completely one-sided.
This is why many OTB classical tournaments have sections. You will get the most benefit from playing opponents within 200 points of yourself and analyzing the games afterward. Here the games will be much closer and more interesting with lots of feedback for both players generally arising in the analysis.
If you are facing an opponent who is rated 700 points above you, the game is more or less hopeless; you are expected to lose! Just focus on having fun and don't worry about the result; just worry about playing as well as you can.
There have been two instances when I had to face IMs in classical tournaments (I was only an expert so this is quite a mismatch!) and in both cases what happened was I just focused on the game, outplayed them, and they were lucky to escape with a draw!
My advice is to thus not stress about it and make sure that you are having fun (otherwise what's the point?)



