There are all sorts of witches. Some are pagans, some are not, some are occultists, some are not. It really depends on what the purpose of one's Craft is.
I am both a witch and an occultist. Part of my Craft is working magic, connecting with the ancestors and Old Ones in a deliberate fashion for deliberate Work.
To do that, I work keys. To work the keys, I must learn them. My Way depends on knowing the proper symbolic keys to open the specific doors I want opened. As long as one knows the keys, one doesn't need to utilize specific words/rites/ceremonies. Yet, we have them, and we use them. The reason some witches utilize scripted ritual is that ritual is a shortcut. Like walking from your car to your front door. You could walk a different way each time, but it's easier if you just walk in a straight line. After a while, your consistent walking in a straight line wears a groove in the lawn, a path which is the easiest way to get to your door. Then, others who come to your house see that path, and they walk it, too.
Rules and laws arise when one begins to gather a clan. People are social. Although solitaries often claim to eschew coven work, they still seek out other witches and attempt to forge community with them (for example, this one.) Once more than a few people come together, rules must be put into play to maintain order. "Laws" come about when it seems that certain ways or rules work well, are logically and or naturally consistent, and become codified.
I think rules and laws are useful, but only applicable within the group they are meant to serve. they are nowhere near "universal."
In my tradition, we have our way. We do things that are internally consistent with our way. If someone wishes to work with our group, they work our way. if they don't, no problem, they work their own way, no harm, no foul.
An example is learning Tarot. I posted to a girl the other day who was annoyed when reading tarot because she kept having to look at the book for the meanings. She got two replies from those who answered her request for help:
1: Forget the book, go completely by intuition, and eventually you may be a facile reader.
2: Memorize the symbols (meanings) of the cards through repeated study and use. Discover what the cards say to you over time. Eventually, you may not need the book, and be a facile reader.
Looks like those two theories apply to witchcraft in general, as well. Both may be true, but all people learn differently. Some do better with structure, as it gives them something they need. Others do better without, as it gives them what they need.
Rigidity is in the eye of the beholder. What some see as rigidity, others see as structure and discipline. What many don't see is that structure is a tool for learning. Once the material is learned (internalized) the structure falls away and the witch is both strong (well-disciplined and knowledgable) and free.