SC Cue.....
I have competed many times at the BigPigJig! It really was my training ground and one of the first contests I attended. I cooked with others, NOT by myself, and learned so much from these folks.
First thing when competing...ask questions...you are off to a good start!! LOL Also, you are cooking for judges..NOT yourself or your friends. So, you better cook stuff that is suitable for these judges. EG..I love my ribs really hot, but would never dream of submitting a hot rib in any sanctioned contest.
So, here is my take on your questions......
1. Sweet, sweet, sweet! Don't even bother with anything else! Yes, judging is and always will be subjective, but the trend of sweet is a given. Also, don't even think about trying anything non-traditional....the judges are expecting BBQ, which is normally red based sauces that are sweet. I have met others who have tried pushing the envelope in taste.....Chinese sauces, tropical sauces, etc. NONE I have ever seen have won or even placed high. I have talked with judges who will mark you down on taste if you use a non-traditional sauce.
More and more of the events are finding Certified judges and they are especially prone to traditional sauces with a sweet edge.
2. On the MIM circuit, EVERYBODY injects EVERYTHING! Even their chicken wings! That is why you see the large injectors...they can draw an unlimited amount of juice from large wash tubs or 5 gallon pails. They need these big units because they cook an incredible amount of meat and they are cooking whole hogs. Shoulders(15 lbers. normally) and hogs take LOTS of fluid!
On the KCBS circuit, as Jim mentioned, you see more and more folks doing this.
The only meat not injected are ribs, but they are marinated for about 6 hours.
Personally, I have tried and abandonded the injecting of my butts. There are some issues when injecting....tracking marks, intense seasoned spots and discoloration of the inside meat. MIM cooks usually cook 10-15 shoulders at a time..with that much meat, you can easily find good meat to enter, but, if you are cooking just one...like most KCBS folks....these problems become large issues.
3. MIM is judged on 2 things......On-site and blind box. The blind box accounts for 60% of the judging score...at least I think that is the current weighting. The onsite stuff can be overwhelming to a rookie..BUTTTT I have been to many contests where guys show up with very small rigs and tent areas and do just fine. You will need to drag around tables and chairs...for the judging...3 judges are invited at separate times for on-site judging in the preliminary round of judging. If you make it to the finals, you will have 3 judges on-site at the same time, so you need room for them to sit and enjoy.
Not sure about the Top 10 as I normally don't hang aorund and see the final, final results. MIM has 2 steps in the finals outcome...Round 1, where everyone competes, then the Finals round where the Top 3 teams re-submit all their meats...hence the large amount of meat that is cooked.
4. When I attended my first Memphis in May event, I thought I was at a Reynolds convention!! Foiling is VERY prevalent on the MIM circuit. I won't say everybody does it, but I feel safe in saying that upwards of 75% foil all their meats.
Now, keep in mind, on the MIM circuit, they only cook pork...NO chicken or brisket..so they are foiling ribs, shoulders and their whole hogs.
Personally, I will continue to foil, especially my ribs. My scores in ribs skyrocketed once I got my foiling times down. I continue to think that foiling results in a superior product and that is what I am after.....damn the traditonalists!! LOL
I would encourage you to maybe consider cooking a KCBS event first and then moving up to the MIM circuit.
Hope this gives you a little info.