What kind of a beach? Is there wave action?
Is it a sand beach? How far is it from waist deep water, where you can sink down to suspend yourself, to land where you can lay tanks down without them being washed about or buried?
For a sand beach here, that is typically 30 feet plus. So being in the water and grabbing your tanks from shore is not practical. Beyond walking in and out of the water in increasing stages of fully kitted up. But you can stage near the water, fully kit up there, and walk a shorter distance that way than from your car.
A way to enter not fully kitted is to put an anchored buoy out and stage tanks out to it in swim gear, then enter with your rig on and attach your tanks. Reverse to exit. I have not done that though. If you can lay tanks on the bottom in 3’ of water and they will not move, do the same but skip the buoy. Maybe use a screw in sand anchor so they do not creep down hill.
With modest surf I enter fully kitted so I am as compact as possible and my hands are free for my fins. I mostly exit the same way. A buoy seems practical here as well. My tanks are small enough, I just enter fully kitted.
I have not entered with more than small breaking waves. On exit, I’ve been knocked down removing fins and washed up and down the beach a few times. That went fine, and I think easier on me as a wide flat thing than as a tall thing that can tumble, fully kitted of course.
With tiny or no waves I experiment with having the left fully rigged and just carrying the right in hand, to carrying both in hand. Fins might be clipped to the harness. Once in the water I’ll leash the tank(s) to my hip to tether them, don fins and mask, then rig up the tanks. This assumes gentle lapping waves at most. To exit, I usually just walk out, but a few times I’ve remembered to experiment and dekitted one or both tanks and carried them out in hand, which is really rather neat.
Kitting and dekitting in the water is likely easier than with gravity at the car, but carrying is likely easier on the rig than in hand, in terms of your hands getting tired.
Rigging one and carrying one in hand is nice as you can stand the in-hand one on the ground if you pause on the way to the water. And you only have one tank washing about around you as you get fins on in the water.
All my sidemount beach experience has been with two tank sidemount with LP50 or AL40 in Carmel (Monastery or Carmel River) or Monterey California.
I think the 50s are better, as they are ‘leave them back and out of the way and forget about them’. The 40s get moved to the front, where they get in the way of walking or lifting your legs up if you forget about them being there. Just as a, let’s say hypothetical, example, tanks in front, trying to remove fins, breaking surf and a nasty exit where you have to climb up a 2’+ tall sand step to get out are not a good combination. Also, SPGs up get in the way of getting fins on and off.