A spider zoan would be powerful, and a mythical one at that since we saw that she can change into normal human size
The silk is a very strong material, perfectly suited as a weapon. It’s noted for its strength but more so it’s extreme toughness, can absorb a lot of damage before breaking. Its up there with some of the toughest man-made materials like Kevlar.[m
There are also species of Spiders that can fly, by climbing to a high place then shoot their silk out to catch wind currents to become airborne. It forms somewhat like a parachute shape that can catch the updraft and disperse long distances, which is what makes it possible for some species of spiders to fly across the Atlantic, some having been found upwards of 5000m up in the atmosphere. In windless conditions there are also spiders who use the static electric field in the air to gain lift using electrostatics of the silk itself. This phenomenon of spiders becoming airborne with silk is fittingly called ballooning, perhaps due to the parachute-like shape it forms.
Spider silk with highly electrostatic properties is generated by the spinning of their silk, and that is used to trap prey and balloon. Luffy won’t be eating his way out of this trap, no!
To me it would be a very powerful zoan as spider silk has great functional strength and tougness, and the potential of a highly enhanced spinning ability of a devil fruit to make the silk even tougher and more electrostatic, this can become weaponised to terrifying proportions!