I think platies might get a little big.
I've had a biorb for about 8 months now. I think it's a little overstocked but all my fish are ok as are the water parameters.
In it I have 1 male fighter, 10 neons, a phantom tetra and 5 other small tetras.
I had to put 6 extra neons in as I put 12 in my larger tank and something started snacking on them so I had to put the rest in the biorb.
if you have the booklet that came with it it tells you how many fish you can put in it. I think it says 15-20 danios or tetras. I'm noy sure about the shrimp, the rocks are a bit sharp and your shrimp would spend all his time on the bottom. HTH.