I read your other posting. Your chameleon is going to be around 2-3 months in age. It will be a very critical time for him/her in that you must have your humidity, temps, water, and food, all working/in order otherwise their health will fade quickly at those young ages.
I would def hang onto the screen cage because you will need it in about five months or so when your cham starts getting bigger.
I have read on the other posts of people having success with those cages at young ages so maybe it would be ok so long as all your requirements are met.
As for drainage. tubberwear, bendable baking pans, etc. get creative with things that you can use as a drain pane. The potted flowers sit inside of the bigger drain pane and the dripper drips onto the leaves, down to the plant, through the roots into the drain pane. Make sure you read about how to repot your plants to make them cham safe.
Are you excited about your first cham coming in???