Welcome to the forum.
One thing you didn't mention is where the material is coming from. Is it seasoned? Since you mention it will be various widths, then I'm assuming that it is from logs that you are running through a mill, then stacking and drying, or buying rough cut.
Pine can be problematic as it is susceptible to greater expansion and contractions then some other woods; it will move. If it is not well seasoned and you don't properly acclimate it to the shop it will shrink and open gaps after it is installed.
Another method you might consider is to use a ship lap joint. If the wood moves it won't be a noticeable gap like a T & G.
Hi, sorry I missed you. I have gone to find myself, but if I return before I get back, please ask me to wait.
Nothing ever gets built on schedule or within budget.
Tool Storage Bait and Tackle, LLC.