Question

Are facultative carnivores similar to the omnivorous as they also eat both the plants and animals

Answer 1

A facultative carnivore does best on a carnivorous diet, but can survive-but-not-thrive on a non-carnivorous one. It prefers not to do that, but when pushed, it will.

An omnivore really doesn't care much either way. It eats what's available, vegetable or meat. There may be personal preferences, but on the whole, the organism is not stressed by being forced toward one or the other.
So we cannot say that they ara similar.