How can I choose the best lag screw / lag bolt?
The bigger question is how many vertical supports and how long are they?  1/4" lags 2” into the 2x4 has 510lb pull out strength (255lb/inch) put 2 or 3 in each piece of strut and each one can handle hundreds of pounds.
5/16” lags 266lb/inch; 3/8"lags 305lbs/inch.  You don’t need a very big lag bolt when using multiples. My examples have a small safety factor added in and these won’t degrade the strength of the 2x4. I usually drill pilot holes,
But not all brands of screws need pilot holes. The depth into the wood is the threaded part that provides the pull out strength over ½" sheetrock I would make sure to have at least ¾" -1” smooth shank that provides the sheer strength as the weak point is the start of the threads.