The 2.00 width Schwalbe Big Apple works the best of the dozen tires I've used on my wonderful Sun EZ-1.
You can overpump to 75psi. I tried the 2.35 width Big Apple -- don't do it! There's insufficient clearance chain to tireside. The tireside will grab the chain and stuff it. The Sun rims are only singlewall and might blow out with a 100psi tire of the 1.85 or greater width. This happened on my Giant Revive using a 1.95 tire at 95psi. Because all the rider bodyweight is directly above the rear wheel, I find it important to have a puffy tire filtering out the road shock. So: 75 psi in the BA 2.00 rolls plenty lively, cushions, has clearance, is puncture resistant and has a reflective stripe that looks good in a pair with a 16 by 2.00 BA up front.