No, it's certainly doable to face a lynel first thing off the plateau, but I would advise against it unless you got some decent weapons to ration durability for their health pool. Most of the people I know who've done it, attempted it in an additional playthrough after familiarizing themselves...
My first lynel I fought was the one I met in Faron, and I didn't know anything but I just stuffed my face with apples the entire time and prevailed. I think the best strategy with them can vary from person to person but don't be afraid to experiment. Just make sure you got a lot of food to...