I have been comissoned to make a cake with letters and numbers like the ones in the cakes above, how would i do it? and what 'medium' what i use? (sugarpaste/fondant/moulding chocolate)

I use gum paste and either precolor it or airbrush it after it has hardened. There are lots of YouTube tutorials on how to roll out fondant or gumpaste into an even rope, then just shape by hand. I also go ahead and stick in a lollipop stick once I've shaped the numbers. Lay out on parchment to dry for at least a couple days and then you've got hardened 3D  numbers you can stand up in the cake. Hth!

I've seen a couple tutorials show bakers to draw the letters or numbers out on a piece of paper, lay a piece of wax or parchment paper over it and "trace" the letters or numbers out with the rolled gum paste.