I use coconut husk chip so suggest the coco soft. Put down about 1-2" of the stuff, it will compress a bit when it dries out.
If you're going to use both, just pour some of each in the terrarium and mix them by hand.
Recently cleaned the enclosure and took a pic:
Warm side hide on left with UTH controlled by VE-300 thermostat, 'cool' side hide and water bowl on right, some foliage and wood at back and sides. Plastic 'background' on outside of the tank.
On top there's a couple of lamps (regular + red) because my place gets cold in winter, and Reflectix bubble wrap; plain old aluminum foil can also be used to keep in humidity.