Good luck with your meet.
For your attempts, I would work backwards. Pick a weight you hope to lift but you think you can, don’t be too aggressive. That is your third attempt. Then work backwards. I find that doing 95% on your second attempt and then 87.5% on your first attempt works well, especially since it is your first meet. It is imperative that you know the form required, particularly the depth on squats and the pause on bench. Youtube search some videos of the Fed you are lifting in so you can get an idea of what is expected.
For example in the above paragraph, if you think you can bench 315 1 time as a best, then open with 275x1 (which should be very easy), then try 300 or so and if that feels good for 315. I like being conservative with the first and second attempts until you know where your numbers are more accurately. In addition being successful on your first and second attempts builds confidence and saves energy for the later part of the day (deads).
You should have a reasonable shot at doing 3 PR’s if all goes well. Usually the adrenaline of lifting in front of a bunch of people at a meet helps you out, especially if you have reasonable work capacity and don’t get tired, and if you choose your numbers wisely. The first meet someone does the unexpected adrenaline is a real factor, as you get more experienced it helps less and less (usually).
Amnonia caps don’t do much (for me), and I would not try something new at a meet. Do this meet the way you train and then try them in training later if you want to.
Regarding tapering, everybody has their own ideas but an easy to follow suggestion that usually works is this (I am assuming the meet is on Saturday and it is a full meet).
Train normally the next 5 weeks. This is for the week of the competition.
Monday: Work up to your opener on squats, do it for 1 rep. Do some other light leg stuff
Tuesday: Work up to your opener on bench, do some other light upper body stuff.
Wednesday: Cardio (walk for 30 min or something to stay loose and promote recovery)
Thurs: Cardio or rest
Saturday: Competition, go and destroy.
Regarding warm-ups, if you are not sure how to warm-up properly you might try this outline. Make sure you realize that for a powerlifting meet the 100% number is actually your opener, so you will usually do 5 warm-up sets and then your opener, second attempt, and third attempt
Good luck, I hope you enjoy it. If you have any other questions let us know.