Sigil magic is a method of magical practice that can manifest things the way a spell would, yes.
There are quite a number of things you can do with sigils.
They can be used on their own or along with other types of magic, for a slew of different intentions.
I used to build sigils off lists of different things I was looking to manifest. I had one list of 5 or 6 different things, and one spell sigil for them, and I manifested everything in a period of 48 hours.
You can add them under candles to add a level of intent. They can be made to represent a situation or individual.
They can be used in sachets, you can add perfumes and oils to them. They can be burned to release energy or kept somewhere to be used as a long-term working.
They can be used to protect, exorcise, draw things in, send things away.
The sky is the limit with sigil workings. They can be used for magical practice, or made for decor and artwork purpose alone.
They really can be utilized a number of ways and made by a number of methods.
These can be used creatively for many intents and purposes.
Part of the popularity of sigils (in their more current understanding) is that it applies the psychological model in a straight-forward method to do magic, while suspending disbelief to let the spooky woo (thanks, Billy Brujo, for that term) to take place if need be.
A sigil is basically a way to create an abstract representation of an intention or meaning such that it does not necessarily register in the conscious mind (again, in the more modern take through chaos magic). The creation through process is meant to embed the meaning into the subconscious of the person who made the sigil, and thus the sigil's intended purpose is enacted without conscious effort or list for result.
So, as to the direct question: Basically, in a nutshell, yes. Sigils and spells are not, in themselves, magic. They are both a means to attempt to achieve a result in the use of magic. You are convincing your unconscious mind that the thing you are doing is equivalent to the desired outcome, and then doing the thing. Therefore, the thing done becomes the means to manifest the result.
One such good example is in the repetition of the statement of intent some people use while creating a sigil, or with the chant or incantation one may use while casting a spell compared to the prayer bowls popular in the Middle East during the Maccabean period. People paid magicians and faith healers for results, and they would create a symbol to draw in the center of a bowl or plate, and then wite either a chant, a mantra, or a story starting at the outside edge of the bowl such that the dish would have to be turned round and round to eventually reach the middle image, and the result desired. The image became an abstraction of what they are reading, and the event, they'd be convinced (indirectly) is directly the thing needed to achieve the desired result. In my opinion, it is extremely similar to the process of creating and using a sigil. Similar can be said for its analogy to modern spells, which are simply more elaborate. Candles may be lit, ingredients spread across a table top, items waved through flame, crystals arranged in an elaborate grid -- and then a chant with intense focus by the practitioner, because that spell means the achievement of the result.
