Can I switch from the third-person camera to the original camera perspective? I didn't really play Subsistence and to me, my perfect MGS3 experience demands that I play it in its original "sorta" over-head perspective.

Click in the left stick and shit bricks.

You can if you click in the right stick, at least you could in the original and there's no reason for them to change that.

Never used it much myself, I thought the newer camera mode felt so much better.

Yes you can. Click the right stick/press R3. Voila!

There's also a switch in the settings, I think.

Also you may pull the right trigger to zoom out ... you end up in the classic angle I think