I would ask a different question. You are obviously working out, and I assume that you have a balanced workout. So, in theory, there should not be any difference between the sides.
If, as you say, there is, then there must be a different reason, and I suspect this to be postural, possibly work-related. The left trap may appear bigger because you may be in the habit of raising your shoulder all the time. That could make the left lat look smaller than the right.
My suggestion is to take a look at this first before you begin with changes in unilateral exercises. This may only exacerbate the problem.
There can be a few reasons why this is happening, but my guesses are a couple of options:
-You overcompensate one side more that the other and I don’t mean during workouts, but rather during your everyday activities.
-Genetics (most likely option)
-Both of the above
There is no way of knowing what the reason is if we can not perform a fitness test/postural assessment and take a look at your workouts. Hopefully someone else here might give you a better answer.
I agree with the other two answers.
You are more than likely compensating one side. Typically if one side is bigger (thickness) then you are pull or pushing more weight with that one side. The reason your right lat could be wider is your hand placement causing you to extend your lat out further than your left making it wider.
A good example would be a pull up. If you want wider lats then you would want to grab the pull up bar toward the edge of the bar extending your arms out further. Or if you are doing a deadlift you would want to reach out further on both sides of the bar, extending your range. This help build Wider lats. Adversely if you are looking to building thickness you would hold the bar with your hands closer. You can lift more weight and it puts emphasize on thickness. Check your form next time. You might be reach farther out on exercises like this with your right arm while keeping your left arm in closer.
IF you want to get symmetrical you should look at doing single arm exercises. You can focus on form and making sure you are engaging the muscles correctly.
You really need to speak with an exercise professional in person. Without seeing exactly what you are talking about, there is no way to make recommendations. Any attempt to do so would at best be wasting time and at worst lead to complications and injury. What is holding you back from seeking personal advice? The cost is nothing compared to the other options.