Yes, there is a difference. You shouldn't be baking a cake (or anything else) in a microwave oven.
A microwave oven excites the water within your food. When you put in dough or batter, the excited water doesn't bind with the starch the way it does under normal heat, it escapes the starch, leaving you with a stone-hard piece of dough or batter.
There is something called "five-minutes microwave cake". I haven't tried it, but in the recipes floating around the interwebs it gets eaten while still hot (so probably before it has had the chance to get too hard). It also seems that there is a very small heat frame in which it gets OK. Bake it too much, and it will get hard, or burn. Bake it too little, and you end up with a mug of warm batter. It is also supposed to be a cupcake, I suspect that if you try to bake a bigger portion at once, there will be enough temperature difference in different zones of the batter to get underbaked, baked and hard portions all at once.
Bottom line: if you want to try for the fun of it, make a cupcake in the microwave, and watch your energy input (microwave watt setting and time) very closely, then eat immediately. You can find recipes all over the Web, e. g. on Instructables. If you want a real cake, don't bake in a microwave.
The right size is important, because baking times are designed for a specific batter thickness. If a recipe is meant for a 26 cm pan and you pour the whole batter in a 18 cm pan, it will be much thicker and the middle won't get done before the top burns. That is why high cakes are made by stacking layers, not by baking one high cake.
You can pour a batch of batter into multiple small cups and have it turn out all right as long as the height stays more or less the same as it would have been in the large pan. My advice is to calculate the area of the pan given in the recipe and the area of your silicone cups, so you can know how many cups to use. You don't have to be completely precise, for the average cake it is not too terrible if you have +-0.5 cm difference in batter height. If the difference is larger, you can still get good results, but you should adjust the baking time.
The resulting cupcakes will still have the thickness of the normal cake, or somewhat more if you use less cups and bake accordingly longer. I would advise against trying to bake high-rise muffins from normal cake recipes. Even a sponge cake recipe might need some adjustment of the amount of baking powder before working as a high muffin. Other types of cake, especially the more exotic ones (genoise, flourless cakes) are unlikely to bake well if you fill them into deep cups.
Best Answer
I make rice in the oven if I'm making a large meal and don't have a burner to spare for the rice. I bake it in an enamel cast iron Dutch oven (you can also use aluminum or stainless steel trays / hotel pans covered tightly with aluminum foil) using the same water-to-rice ratio (2:1) as when I make it on the stove. Cook at 350°F / 177°C for approximately 20-30 minutes, remove from the oven and let it sit, covered, for another 10 minutes. Fluff with a fork and serve!
(Note: The cooking time will depend on whether you pre-soak the rice and also how good your oven is at maintaining a constant temperature. You can check if it needs more time by wiggling the pot/tray a little; if you hear water sloshing around, it needs more time, but if it feels like a solid mass, it's probably done.)
The only problem you might have with this: sometimes the rice on the bottom of the pot gets dried out and sticks to the pot. You can avoid this by boiling the water before you add the rice (on the stove, but I guess you could do it in the oven, too. If you have an electric kettle and you're making a relatively small amount of rice, you can heat the water in the kettle and just pour it over the rice, too).