IMO as you have only been to Epcot once in the past, I would tell you to buy a 5 or 6 day park pass for your next vacation. This will allow you to spend a full day in each park (and believe me each one takes at least a day to enjoy) and then an extra day or two to just enjoy your favorite things. This also allows you extra time in the parks just in case you cut your other days short to go back to the resort and enjoy it as well.
As for the resorts well there are so many options. I would tell you to make at least a weeks stay if you can afford it. You may also want to switch hotels mid stay. There are 4 levels of Disney resorts: value, moderate, deluxe and home away from home. You may want to stay in a value or moderate for the first 3 or 4 nights and hit the parks hard on those days and come back and spend a brief amount of time in the pool at your hotel. Then you spend the last 3 or 4 nights at a deluxe and spend more time relaxing at the parks than running the parks. If you decide to move to a different resort midweek, your resort will move your luggage to the next hotel for you. Bonus in moving is that you get to enjoy two completely different resorts, however, downside is that you have to move midtrip. Believe it or not tons of people do this.
As for the best time to go, it is basically anytime that the kids are back in school and its not too hot in FL. Basically Oct. to mid February (peak season begins in mid February and that is when prices are at their highest).
Your going to get so many different options. As for nice pools, I love the moderate resort of Port Orleans Riverside, pool is nice with large slide and a play area that looks like fort. The grounds are peaceful and beautifully manicured. Believe it or not you'll enjoy the small walks even after a day trekking through a park. CS also has a great pool area and is also nicely manicured. As for Deluxes, I do love WL (and wish I could afford to stay there more often). Many others will tell you that SAB at YC/BC is the best and I have toured the property and seen the pool area but can not afford to stay until I win a lottery. The pool area is beautiful and really does seem to be a lot of fun.
There can be plenty of fun in planning a trip so enjoy and don't become overwelmed. Take each area and just make a decision and stick to it.