The demonstrated one is fluid - stylistic curls in a spiral within a circle around a blank space in the middle. A symbol appears in that blank space when something is sealed into it.
The easy way to do storage seals is to define what you'll be putting in it - iron or gold or water. The hard way to do storage seals is so that it'll adapt to anything you put in it, with limits on that making it easier (so you might have a 'metals' seal, which is harder than an 'iron' seal but easier than a 'solids' seal).
That really, really varies with the seal. Some are unconscious, as far as they can tell. Some are left conscious but trapped in a mindscape, or in a separate dimension.
An efficient seal uses very little space, fewer symbols, and less chakra. She can demonstrate the difference - here's an inefficient 'iron' seal, which is full of unneeded buffers and contingencies and definitions. A complete novice might find it useful, but it's better to leave some of that up to the sealer to do. Here's an efficient 'iron' seal, which has extremely few symbols and does what it's meant for as cleanly as possible, nothing else. (It's better to have two efficiently designed seals than one seal that does both functions, too).
Most seals, if messed up, will just explode when you attempt to activate them. Usually if you don't overcharge them this explosion is small, just enough to set the paper on fire. Storage seals sometimes mangle what they're meant to be storing.
Getting a sense for if a seal is going to work is kind of like getting a sense for if a particular arrangement of words is a valid sentence in a specific language. You can underchannel a seal, and feel out if there's any - sort of eddies, where chakra is getting stuck or flowing incorrectly, but not all seals can be underchanneled and still work at peak performance, and that sometimes misses more exotic ways of screwing up.