Yes, your surface finish is limited by your print quality - but smoothing surfaces post-print goes a long way. "a lot more difficult" doesn't mean impossible at all, but you will have to remove more material to flatten the surface before you can start polishing. Coldworking (cutting and polishing glass) is a field in of itself, and requires some non-trivial equipment to do efficiently, so I would recommend designing your initial pieces to avoid much coldworking. Don't expect an optically clear surface anywhere the glass touched the mold - the default for investment cast surfaces is matte, and clear surfaces either need to be polished with abrasives or HF+H2SO4, or were the top of an open-face casting.
Unfortunately, most kiln-casters prefer very high lead glass (40%+), because it flows very well and doesn't devitrify easily. This, however, makes coldworking an environmentally-dicy proposition, as it generates lots of micron-scale lead dust.
A microwave may suffice to fuse small glass jewelry (...kinda, the annealing will be pretty horrid...), but isn't going to cut it for casting. Stuff at the scale presented in the article would require firing times of at least 12 hours, with much better temperature control than a microwave can provide.
Unfortunately, most kiln-casters prefer very high lead glass (40%+), because it flows very well and doesn't devitrify easily. This, however, makes coldworking an environmentally-dicy proposition, as it generates lots of micron-scale lead dust.
A microwave may suffice to fuse small glass jewelry (...kinda, the annealing will be pretty horrid...), but isn't going to cut it for casting. Stuff at the scale presented in the article would require firing times of at least 12 hours, with much better temperature control than a microwave can provide.