How hard is it to move from trynd to fiora/riven

I'm a trynd top main. He works good in bronze. I usually win lane Except Vlad, heim, the fucking devil, and mabey mundo but never tried Vlad or mundo. I hate those 2 in general but I will get mm 3rd item to stop them. I truly to all in early under the right parameters. If they push to my tower, I lvl 3 all in and usually get a flash/kill. I only tried fiora and riven once.fiora, didn't snowball or feed. Riven, got 1st blood but lameswap and now I'm against the donger since it was a ziggs top and feed because bullshit. That was a long time ago but in general, if it's not a hard lane, they get rekt by my trynd. I'm actually thinking about practicing riven and fiora in normals then ranked. Before you say fiora is a noob champion, nope she isn't. You need good decision making, rito made her even harder than she originally was, and needs an early kill like riven. Trynd doesn't since he farms and split pushes. These 2 snowball and can actually carry dem gaymez even harder. But how hard would it be for me to learn one or both of them. (Yes I do take our team comp and theirs into consideration and play a tank if we need one)