If you want a left side charging handle you would have to buy a spare bolt carrier from Checkpoint with the handle milled on the left. These are new production from CSA.
When I bought my Vz 58 directly from Checkpoint they were in stock and went for that option which cost extra, but less than the price of a new bolt carrier.
As far as heat shields, you might try something like self adhesive tape for car engines like Thermo-Tec (I haven't tried this myself).
If you think the black polymer hand guards heat up, that's nothing compared to the phenol+wood chips (beaver barf) those things get ripping hot! (They look neat and historical but I don't use them).
As far as optic solutions, I would recommend the skeletonized side optic rails sold by Checkpoint; they work just as well, and are considerably lighter than the standard rails. I bought the standard ones first and was surprised by how heavy they were. I never installed them and returned them for the skeletonized which weigh about half as much.
As for the optic mount, the cheaper option is the CSA mount sold by Checkpoint or the the nicer option IMO - the RS Regulate. Both will work fine.
I went with the RS Regulate VZ-304M with the AKML (Aimpoint Micro) for the Holosun & Primary Arms red dots that I already own and think that it is fantastic. RS Regulate isn't cheap but it is the best out there.
If you're going to have an optic mount with a folding stock, I would recommend a right side folder.
Keep in mind that with a side rail and optic rail installed on the rifle, you looking at at least 3/4 inch sticking out from the left side of the receiver which might prevent you from properly folding the stock.