Possession limits apply outside your home. In your home, you're allowed to posess whatever you grew. As you indicated, sales are not allowed by private growers in Colorado.
A stealth cabinet would be best. You're trying to reinvent the wheel, to get satisfactory results you will spend more on the dresser than to just buy a plug n play system. A stealth cab will not broadcast the intention, much less than a dresser with light pouring out of every crack, seam and vent.
I use 31 gallon. More nutrients = less flux = longer intervals between change outs. Pulling a root ball the size and shape of the 31 gallon tub makes for greater yields. More root, more fruit.