The A2 handle provides extra rigidity to the upper. Its not a material difference as far as material type but by removing the carry handle you remove material which will make it slightly weaker. That said the trade off was worth it in the modularity department.
The Chrome Lining was added to barrels for a few reason. Fisrt it increases barrel life, it helps reduce corrosion, and it helps in extraction. But it does slightly reduce accuracy
As a current civilian I can choose whatever barrel I want and stay with 4150 CMV. The issue with SS is heat affects it more than 4150 steel. It is softer which helps make a more uniformed and correct bore when they button rifle it, but because it is softer it does not handle abuse and heat as well. This will lead to shorter life than a 4150CMV barrel as each bullet reduces the rifling.
SS barrels are generally used in DMR's such as the L129A1(LMT 308MWS) as a designated marksman rifle will not see high volumes of fire.The increased hardness of 4150CMV gives it far greater life than SS but at reduced accuracy because the rifling will not be as clean since they are harder and the metal is affected differently when button rifled. Now 4150 barrels are still 1MOA barrels but SS can be .25MOA barrels if you get a good made one.
I personally like to avoid cleaning rods unless they are polymer. Alot of people jam them in which bends them and causes them to scratch the chrome lining greatly reducing accuracy. If used correctly they are fine but far to often they are not use right.