If the boat has always been stored like you mentioned as well as trailered and doesn't have any damage, I would expect it to be in at least better than average condition, if not greater. I don't have much experience with the 225 Tournament of that vintage other than to say yes, it has your standard marine grade plywood as opposed to the Greenwood XL. On top of that, the 1991 model year is going to be an SeaV1 hull design and before they changed over to the SeaV2 hull design the next year in 1992. In regards to what you should look out for on the transom/transom bracket itself, I'd say any damage or cracks, if the outboard transom bracket has any leaks and is full of water or if it's bone dry. I'd also look for flex both on the stern of the boat as well as the transom bracket and/or swim platform if it has one and so forth when raising and lowering the motor as well as acceleration. Also, you can always go over the boat and especially the transom area with a rubber or plastic mallet and tap to see/hear/feel any duds or soft spots, which would indicate water intrusion. Other things that will indicate water intrusion would obviously be damage and cracks as mentioned above, as well as rust or dark colored stains and seepage that could be coming out of the hull.
One of the many things I love about my boat is that it's the same as yours where it has the fully enclosed transom as well as the transom bracket as opposed to the bang cap or transom plate. In theory, you would think that it should make the transom that much more enclosed and not allow any water inside. My boat had/has no water intrusion and the transom is still sold. Hopefully the owner is being honest and forthright with you by giving you accurate descriptions of the boat and anything else included in the sale and you should be able to confirm that pretty easily without bottom paint on the boat. I always recommend having an accredited marine surveyor inspect the boat with you so that you can get a "professional" opinion on the matter. They usually run $500-$1000 but can save you headaches in the near future by pointing out what will need to be replaced and how much it will cost. I personally am curious though as to why this specific year and model of Grady White? If I were in your shoes, and especially if the boat turns out to not be in the condition it's advertised to be in, I'd look for something newer that is a SeaV2 hull and has the Greenwood XL in it, as opposed to the former. Just my opinions of course. I'd also mention asking price, location and so forth to make sure you're getting at least a fairly decent deal on the boat. Either way, good luck.
