Can one use plastic props or something similar or is that frowned upon? Has anyone used those on cakes they made for others? I have no experience with fondant and not quite ready to use it. I do want to make a Christmas cake and am thinking of using plastic props or something similar.

always try to get something that is safe for food-contact. hobby stores have super cute cupcake picks / toppers nowadays.

Yes, there are many things one *could* use but not all of them are safe to be used on food - even if you bought them in a cake supply store.
Not that I want to talk you out of using plastics but.....fondant is sooooo super easy to use for flat, lay-on decorations and a few simple shaped/3-D items Think PlayDough or Pie dough. Just roll it out and cut with a pattern or cookie cutter. To make candycanes, just take a small ball (about the size of a walnut or smaller and roll between your hands until you have a snake whatever length you want; shape the crook and allow to dry overnight.
You can make a Christmas tree from a ice cream cone. Pipe b'cream stars or leaves all over it in green then make tiny dots to look like lights and ornaments.
Hope these suggestions help you.

Thanks, I never thought of using an ice cream cone. Very creative.