Re: I saw a ghost pepper on the store, is it just seed packets or unlock the plant?

If the offering is for seed packets, then I do not think the plant is included. (these offers are for players who already have the plant a chance to level up)

If you press the information button (the little in a blue circle) on the top right corner, of the item on offer, it should tell you exactly what you are getting.  

Unless there is a recent change, Ghost Pepper is a Gemium plant, which you will need to buy it with 100 gems from the green (Plants) tag in the store when it is available.