I’ve been to Frontenac (an expert kayaker buddy of mine is in Ontario and buys his boats from them) and they are an excellent and knowledgable outfitter. I would put a lot of value on their assessments of boats.
The problem with shorter boats is that they have to be comparably wider to provide enough volume for displacement, which becomes even more problematic with a heavier paddler. I’m only 5’ 5" and 150 lbs. I currently own 5 kayaks which are 12’, 13’ 6", 15’, 15’ 7" and 18’. I only use the 12’ one for small lakes and narrow slow streams and to take on airline flights because it is a 22 pound folding kayak that packs down in a duffle bag. I never take it out where I want to paddle any distance or with people with longer boats. Virtually all 12’ boats are slower than longer boats, even those only 18" or 24" longer. In my other kayaks (the 13’ 6" and 15’ 7" are both also folding kayaks, and the 15’ and 18’ are hardshells) I can easily cover distance and keep up with anyone else I am paddling with.
Putting your wife in a shorter boat than you are in will disadvantage her in keeping up with you when you paddle together. A lower volume longer boat will give her more speed with less effort. Unless she is very petite, the Tsu 140 would be a good choice for her. The Tsu 120 is a kayak for older children and very short and lightweight adults.
“Recreational” kayaks (mostly 9’ , 10’ and 12’) are for what we call “lily-dipping”. They are for short day trips close to shore on calm waters or for leisurely floats on smaller rivers. They can be quite fun and they are all some people need. But some people get bored with them pretty quickly. If you want to feel the pleasure of covering some distance or going out on larger, windy lakes or coastal conditions or even just longer rivers, a longer boat is much more enjoyable. There are facts of basic fluid physics that mean that a shorter boat has a speed constraint beyond which even a strong paddler cannot accelerate.
To place it in an approximate automotive context: rec boats are golf carts, 14’ “light touring” boats are commuter sedans, 15’ and 16’ touring boats are highway cruisers and narrow low profile 17’ and 18’ sea kayaks and surf skis are sports cars. Obviously, there are many exceptions to that (some expedition touring kayaks are more like Mack trucks.) But I think you get the idea. If you can make it to an on-the-water demo you will quickly get the feel for what we mean about the differences between shorter and longer boats.