I have used both those canvases, but not on the 8300.
However, the Watercolor media type is probably optimal. For 901, you want highest head height and strongest vacuum. 777 is possibly the smoothest and lightest weight canvas out there, so perhaps you can take height and vacuum down a notch, or simply use Auto.
Make a few test prints and very closely examine the peaks of the canvas texture to see if you are getting head swipes. If so, increase the head height setting, and/or the vacuum.
For ink load use Medium. From the limited testing I have done, matte canvas does not much benefit from heavier ink loads. If you are new to canvas you probably feel the test patches and calibration patches are looking pretty ho-hum in terms of density. That's just how matte canvas is. The apparent density and contrast will increase a lot when you coat it.
Create a profile from the the patches first without coating, then with coating. Make some test prints, coat them, and see which ones you like best, and don't assume the coated profiles will be better.
Before printing your calibration patches be sure to run the Media Configuration Tool to get the feed calibration exactly right. It has an effect on patch density, and of course so does ink load.
FWIW for a long time 777 had issues with the edges of the rolls being slightly curled in a way that created head swipes along the edges. I assume that has improved by now.
