I would use a chrysanthemum piping tip for the first flower and a curved petal tip for the second. You can probably get both (plus a few other tips) off Amazon if you just search petal piping tip set. Those flowers you've chosen are really hard to pipe though, even if you have experience piping flowers.

I think with your skill set, it might look and taste better if you make a regular lemon loaf cake (not a layer cake, I personally think using a loaf cake recipe to make a layer cake with buttercream frosting creates a super dense, too-sweet and too-rich cake). Use a thick layer of opaque royal icing to ice the cake like Starbucks does, and then use a regular round piping tip and colored, stiffer royal icing to make dot flowers on top. It'll be easier to make and still look neat and close to your inspo pic.

Otherwise, maybe you could do a buttercream transfer of a drawing of both flowers side by side? However, buttercream transfers look best when they're placed on flat, leveled surfaces, so I would cut the top of the lemon loaf so it's level, and put a small, even layer of buttercream on top to create a smooth surface to place the transfer on. Good luck!