I didn't, so can't answer your specific questions, but I'll weigh in anyway!
I have offered advice to others to stake out their pool, and one step farther. Plot out chairs and chaises and tables, etc. Where the deck is going to be. Landscape areas. Everything. Simulate as much as possible. Add in a few floaties, in and around the pool, etc. Sounds silly, but I don't think it is. Get everything in place, then sit around your "pool" and walk around the floaties and chairs and table, etc. Stare at it for a few days, from your yard and from inside your house. All those things, in and around the pool, take up way more space than you would think (especially floaties, chaises, and tables with chairs). Now is the time to see how everything fits, and feels, and then adjust accordingly.
The counter to that: pool size is personal preference + practical need (what you want to use your pool for, and by how many people), but the bigger the pool the more it costs. Not just in terms of initial construction, but in maintenance, too. More chemicals, more brushing/vacuuming, more cost come re-surface time, etc.
Have fun with it. The more you plan, the less surprises later!