Camellias are mostly slow-growing shrubs that can last centuries and never stop growing. Thus, some pruning would be required every 3-5 years or more in order to keep their height in check. Exactly how often you need to prune depends on how slow/fast the shrub turns out to be. Any of the camellias that is good in your zone should do well in Houston. Just prune their tops off with some regularity once they reach the desired height. The Gulf Coast Camellia Society suggests that you try to purchase the plants grafted in C. sasanqua root stock if possible. See the link below, Luis

Here is a link that might be useful: Gulf Coast Camellia Society

I would suggest shi shi gashira, is a well known for being a spreader although it will eventually get some height but I think it would do great for you. I worked in the past for a couple that had dozens for foundation planting and they worked great for the situation. They have the same cultural requirements as regular camellias. they are also pink.