Ok, so I have edited almost every player in league, and here is what I have found:
QB
Take off flack jacket
put on back plate
For most QB;s their chest and gut are at lowest level but are actually the biggest. Another detail that makes no sense and has been this way for years. Usually when you take something down, it gest smaller, but the dev's at Madden don't get hung up on details like that. But I do.
So take the chest value to the far right and gut up as you see fit.
You can make the calves bigger, and although it will default to 0 (far left) the calves will stay a little bigger.
Now before you change the weight, back out and save the player. Sometimes when you lower the QB's weight they get bigger, sometimes they get smaller. So just play around with it until you find what you are looking for.
RB
Unless you want them to get significantly smaller, do not change their weight. Take off back plate, and change to small pads, and then same for QB, take chest level all the way up and adjust gut as you like.
WR & DB
DO NOT CHANGE THEIR WEIGHT. If you do this they will get bigger, and their shoulder pads will get be huge no matter what you do, especially if they are a smaller receiver. The weight has no bearing on how a player looks form 160lbs, to almost 250lbs. It is pathetic and I have no idea how it hasn't been fixed. The people that make this game pay such little attention to the little things it drives me crazy. I should not be more into making the game better than the people that get paid to do it, but here we are.
So chest and gut maxed, and once again do not change the weight.
TE
Take weight down a little if you would like here, but a warning, they will all look kind of the same, but it does look a little better.
Chest maxed, gut as you wish.
OL & DT
Be careful with the weight here. Once you get to 322lbs, the player model changes a lot. If a player is 295lbs - 320lbs, I take them up to 322 and adjust the gut to make them look a little more realistic. If a player is over 320lbs I don't change the weight and adjust the gut.
Now you want to take chest all the way down, because now moving the chest and gut levels down makes them smaller, this is insane right? How do these people have jobs. I could have this cleaned up in a week.
DE & LB
Most of the time I just take the weight down a little, and same as the others, chest maxed, and gut whatever you like. It is hard with the players in this weight group because once you get the weight under 250-260, they really don't change much so this one is more of a preference thing.
Well I know this isn't perfect, but it is something. Hope this helps a little. The player editor had always been bad, but this is the worst I have ever seen. I am obsessed with making players look like they do in real-life, but this year it has been a challenge to put it nicely. Most years I just have to adjust the weight, and that takes care of it, but that is not the case any longer. It is impossible.
I think the main problem is the shoulder pads on the smaller players. This is really bad because WHO wants bigger shoulder pads on players? NO ONE, but there are large and extra large shoulder pad options, but not extra small. This is another detail that if the people who make the game actually watched just one football game they would know that players all have small shoulder pads. Every player. The other is the chest size on smaller players. This is just a mess and they need to fix it. I'm done because I am starting to get angry.