The one plant I can think of that would look right and do well in this setting and be fire and deer resistant is Yucca filamentosa 'Color Guard' or 'Bright Edge'. Listed for zones 4 to 9. I know you have to have a real winter of some sort in that setting and location.

I think the panels look very peculiar. What are you trying to hide?

Sorry, I have no help to offer, but am curious if you want fire resistant plants why you put up wood panels? Seems they would be the first things to catch fire.

IMO that hill will need some terracing if you are planning on enlarging that patio . You will require a reatining wall with drainage ot the patio will be full of mud everytime it rains. The fences are kind of interesting but do not really serve a purpose . This is agreat projet to do DIY but you need some pro advice. These pics show a slope similar to yours where we cut back into it and did a reatining wall done for perfect drainage , lots of ahrd work but doable and the bonus is spaces you can actually use.

The hill you see behind the railing is really too steep to be useable without going into my neighbors property. BTW the ivy has now completely covered the wall