Artificial plants are okay, you just have to clean them sometimes. It may be easier to set up a tank without live plants, but a well set up live planted tank may have to be cleaned a little less. Frogs aren't exactly careful what they grab when they're hunting insects so that's why moss is sometimes not the best choice. If you still want moss you can lower the risk of the frog getting stopped up by feeding in a bowl or with tweezers rather than having free-roaming insects. Generally anything big enough to fit in a frog's mouth but too large to exit easily can be a problem and there are lots of posts by people who've lost frogs to impaction.