So right, I wouldn't use both. The Osmocote will release slower, which is good for slow growers like cycads. and you won't have to re-apply it every few weeks, so I'd go with that.
As far as watering, cycads grow in the ground here, and in summer sometimes get rain every day, so once established, they can take lots of water as long as the drainage is good. But a newly potted one, you might want to hold back a bit until you start seeing new top growth, indicating the roots are growing.
It also depends upon the air temperature, humidity, and how sunny it is. You might want to spray the foliage sometimes if the weather's hot and dry, and especially if it's windy, hot and dry. If you're getting that 'marine layer' fog, well nature's doing the misting for you.