This is my personal opinion and recommendation as a cake designer and judge, on a few questions asked by students.
I always recommend to my students when entering competitions to write detailed description of techniques used on your card, pictures when in doubt; especially if you are using a new technique that a judge may not know how to do or know about.
The problem, some judges do not know all techniques and in some shows, they will let things slide.
As an owner and head designer of two high end wedding cake shops in San Diego we had to deal with fresh flowers in which some are toxic and done by floral designers who have no clue about food safety or placing heavy arrangements or gum paste flowers on the sides of a cake.
I was taught over 30 years ago, all flowers need to be made into arrangements in containers or corsage sprays; ribbon bows placed or nylon Tulle between the cake and flowers, making sure flowers never touched the cakes and all stems had to be wrapped in floral tape to allow no cut stems touching the cake, due to toxic open cut stems; never sticking flowers or wires into cake and only using items intended for flowers to be stuck into cake; I would personally use the glass flower stem holders which could be sterilized.
To be totally honest, in all reality ribbon and tulle are not food safe either, but safer than wire, floral tape and toxic flowers; only ribbons made food safe are accepted.
As for holding flowers onto the side of cakes, I personally do not like wood toothpicks, cookie sticks or dowel rods to be used, I will only use white popsicle sticks coated with white chocolate to prevent from softening in the cake and white chocolate coating to adhere flowers or other items to a cake; which will set immediately on a refrigerated cake, fondant, whip cream/non-dairy and buttercream cakes.
These methods have been tried and true used by me for over 30 years of designing and delivering many cakes; our busy seasons were hot summers 30 mile deliveries with up to 10 different style fondant, whip cream and Buttercream cakes with royal and gum paste flowers attached to all cakes riding in the delivery vans and cars. My main account in SD was the Horn blower Cruise line- known for Harbor Wedding Cruises, cakes had to withstand delivery and rough waters at times.
My overall motto as a cake designer and judge is; if it can be done safely and on a real cake and withstand deliveries, and then it can be done on competition cakes as well. Also, would I eat something decorated that had a wire, wood stick or fresh flower placed into the cake? Is everything used, something that I would find in a safe food establishment? If not, then it should not be on a cake!
One more word of advice to my students, I recommend they all attend a real floral design class, as my first instructors recommended to me, as well. I attended an 18 week all type floral design class, including all wedding designs. I hope my insight on the subject is helpful and again my personal opinion. Feel free anytime to ask any questions. This is how we all learn.