OK, two things that nobody else has addressed:The tank I am contemplating is going to be between 15 and 30 gallons. I am going to focus on plants in the beginning. Down the road I might put in some small shrimps and schooling fish to complete the look and habitat.
What are my options in terms of CO2?
1. Your other option regarding CO2 is "No Added CO2". Although I have pressurized CO2 in my display tank, I add no CO2 to my 20g grow out tank. Anubias, java fern, mosses and occasional swords have been happily growing in there for years. Other low-light, no CO2 required plants include most Crypts. Bottom line: In a low-light tank, CO2 is optional, but it accelerates plant growth. In a high-light tank, CO2 is mandatory.
2. You mention adding fish or shrimp later. To be clear, without animals, your plants will not have a source of nitrogen, and you will have to add it. You will find it much simpler to start with some fish. It would be tough to add enough Amano shrimp to do the job, although 2 or more per gallon would do the job.