I had awesome success with our very first trip using the plans from the book. This was back before the website. I went with an aunt who goes frequently in the off-season, but had never used a touring plan before. We went in a moderate time. It wasn't peak, but it was by no means the off season, way more crowded then she had ever seen the parks before. She kept commenting throughout the whole trip how much we were getting done and how much we were walking straight onto rides or waiting a very short time for them. She just couldn't believe it. She said she'd never done this much this fast on any of her previous trips even if the parks were overall less crowded on those trips.
The plans basically kept us 1 step ahead of the crowds or in a different part of the park from where the crowds were. It wasn't that there weren't long waits for rides, there were. It was just that there weren't long waits when we walked up. We'd come back by the same ride later and see a 30 minute wait posted or more.
Now, however, I'm not sure how effective the plans are because I don't know that there is enough data out there yet to really understand how FP+ is effecting crowds.
It really depends on what type of planner you are. I plan out every single ride in order, so TP is a huge help. If you aren't into that level of planning, I think easywdw for park day recommendations and a little research on which rides are headliners should be enough for a Sept trip. In the fall after school starts, most rides don't have long lines to begin with. It's only the most popular you need to worry about. Schedule FP for some of those and hit the other ones at RD, and you really won't need to worry about the rest of the park. It should average about 20 minutes or less. When TP plans really comes in handy is in the peak season not the off season when you can walk on most rides to begin with anyway.
Besides the plans, TP has great time charts that give you estimated wait times throughout the day by date for each attraction. They also have good attraction descriptions and helpful touring tips, but most of this information is in the book. I think the book is a great investment for a first time visitor with lots of helpful interesting information on everything from restaurants to parts to resorts.
If you want to plan in detail, personalize schedules, or use their lines app for while your in the park, you need to purchase the TP subscription as well. Book owners get a discount.
