I’d like some advice to connect the main panel to the conduit. It’s 2” conduit to the outside which connects to a detached garage. The problem I’m not sure of is how do I go from this LB box to the main panel without hogging out the entire 2x4’s in between the two. It’s 2” conduit because a bunch was given to me. I’m running 3- #4 and 1- #6 through this.
Given that you're using "free" 2" conduit, you have to pay the other way - by basically obliterating your 2x4s to make room for it.
Another option is to downsize the conduit where you go through the 2x4s. Your wires can fit in 1" Schedule 40 PVC conduit (using Sch 40 is OK here). You might consider bumping to 1-1/4 or 1-1/2 EMT conduit, if your existing holes have the space, because that would allow upsizing your wire - either for more amps or going aluminum wire to save money. You definitely shouldn't waste money on copper feeder wire, unless aluminum just won't fit.
Could you cut back the two 2 inch conduits on the right of the panel and set a PVC junction box (ON THE OUTSIDE) and then run conduit over and LB through the wall inside to the back of the panel?
And if you wanted to add any additional circuits in the future, you would have access to a junction box on the outside to come out of. Remember to seal and close (caulk) all the holes and pipes extruding to the outside.
Or just 90 over both 2 inch PVC conduits and then go through the wall into the back of the electrical panel. You will have to re pull new wiring though because the existing would be to short.