Recently had someone request both of these cakes. Both look like bc, not fondant, but I could be wrong. I've never attempted such cakes, so I'd like some tips/hints/advice from anyone that has made something similar. TIA!

i am baker has a great tutorial on a ruffle cake that looks similar to your second picture 

    http://iambaker.net/christmas-tree-cake-tutorial/                                      

All you do is use a rose tip...
 

Yep it's a petal piping tip (104 or similar will work well) for both I think.  Melody of Sweet and Saucy has a great video for the method for the type of ruffle in the 2nd photo on Youtube: 

Here is another tutorial for the first type of ruffle but like remnant3333 said about her video link, you'll need to adjust to have the ruffles facing down not up: http://bubbleandsweet.blogspot.com/2012/05/how-to-make-ruffled-buttercream-rainbow.html

AThose are both sweet and saucy cakes. Watch her video and practice, practice, practice.