Hi,
Question 1: A case for the system specified.
Choosing a case is tricky. This is due to that different people have different plan on how they wish to upgrade their computers. Let me give you an example related to this build. Since you have specified that you won't be using 3.5 inch HDD, this means the only way to upgrade storage is by 2.5 inch bays which implies that you will be upgrading using SSD.
NOTE: Although 2.5 inch HDD exists and available, I do not advise using them since they are very prone to damages.
If you plan to switch to full custom water cooled system, you have to ensure that the case is big enough and has enough fan mount points but what if you want a small sized case to fit a specific area? Or want it to have a fancy look rather than being robust?
I think this is a personalized decision and therefore I recommend you either providing more information on how you wish to upgrade in the future or go to http://pcpartpicker.com/parts/case/ and use the filters to narrow down your search.
Question 2: GPU Cooler?
Depends. If you got extra money to spend and have the technical knowledge on how to build and maintain a custom water cooling system, the latter is an option. Unless you're overclocking your GPU, I don't think it is necessary to have a custom cooler. http://www.xs-pc.com/waterblocks-gpu/ - Take a peep at this website if you are considering it.
Question 3: CPU Cooler
CPU cooling is much more critical than GPU cooling and therefore I recommend using a better cooler than the stock version. If you considered to water cool your GPU than water cooling your CPU makes sense. You can still use a closed-loop water cooler for the CPU if you don't want to water cool your GPU, although this option is more commonly used where overclocking is pushed heavily. A good air cooler should do the trick for light overclocking.
There are two approaches when buying a CPU cooler. You either decide the case first and find a CPU cooler which fits in the case or vice versa. With this said, I can't choose a specific CPU cooler yet
http://pcpartpicker.com/parts/cpu-cooler/#w=0&sort=d4&page=1 you can use this page to help you narrow down your search
I'm sorry if I haven't provided a direct product what to buy, but such parts are better chosen by the user himself since these are user dependant and not critical. Feel free to post what products you have chosen and let the community confirm.
Regards,
Brandon