For what is it worth I have actually found that plants are easier to keep in large vs. small cages. Much easier, actually. But I assume the species of lizard in question has the most to do with this.
In general the biggest problem with keeping plants in the vivarium is lack of ventilation. I think we get too obsessed with keeping in heat and humidity that the air gets stagnant. This is probably one of the biggest differences between US and European breeders. They use significant amounts of ventilation and even add fans and other mechanical devices to move the air. They have great success with their herps and their plants.
Also, I have had best luck with fake plants from "Hobby Lobby" and other craft supply stores. Once a year or so they have closeout sales and I go buy bunches of them. Much better to pick them out in person from my experience. You also save a ton on shipping. Most important is you can see in person which plants have little plastic loops and other dangerous things for the herps.
In fact it's usually this time of year they have the sales...