Yes you can have lower and higher point days by incorporating your 35 flexpoints into your minimum daily point target.
You can choose to use all of your flexpoints per week or some or none. You can't carry them over from week to week though. So once the week is up and you start your new week you get only the 35 flexpoints and your minimum points per day.
Some people use the 35 flex points in 2-4 points per day on top of their mininimum and some people save the points for a special meal or for the weekend when they know they will be going out to dinner or to and event where they will need them. It is entirely up to you but you do have to track them.
When you join WW you get the Welcome book and some materials but you don't get everything at once. Each week you get a new booklet with different materials.
You can also purchase the Foodpoints book and the Eating out points book at the meetings which are really helpful and that I use all the time. I think they are $5.00 to $10.00 depending on where you are located (they seem to be pricier in Canada) but I found them to be worth it for menu planning and being able to make better choices when eating out.
I also have quite a few of the cookbooks which I totally love and use on a weekly basis