As far as the gpu block goes it all depends on which version of EVGA's GTX1070 you have and if it uses a reference pcb or custom one. On the up side you should be able to pick up a used 1070 block very cheaply now. The GTX1070 is a pretty cool running card but what I found once I had watercooled mine is that it boosted much higher and stayed there instead of fluctuating all the time.
A lot of cpu blocks are stupidly priced now due to RGB and people for some reason wanting the inside of their pc looking like a fairground amusements arcade. There is no need to spend £80+ on a cpu block. Having RGB does nothing for a blocks performance which should be all that matters.
A lot of people swear by EK but after shoddy quality control and a abysmal customer service experience when I had a brand new gpu block and a nearly new cpu block leak from the seals I will never touch anything to do with EK again. Take a look at Aquacomputer, Alphacool, XSPC and Watercool's Heatkiller range which are all excellent choices.
Go for the biggest radiator you can fit in your case and the best you can afford. Argueably the best are Hardware Labs radiators and the quality is excellent. Generally, the bigger fans the radiator can take the quieter you can make the system. I switched from a pair of mid range 360mm rads with 120mm fans to a pair of the best 280mm radiators and 140mm fans last year and the difference is night and day. My fans run at a almost silent 780rpm while at the same time having a pretty decent amount of air running through the rads.
Pump, you pretty much have a choice of a DDC or D5 based pump. I prefer the D5 and have a pair of Alphacool VPP655 variants. They are compact and powerful and you can get manual ones like mine that you set the speed by a dial on the rear or you can get PWM versions. The DDC can run very warm which is the reason there are several heatsinks available for them. In my opinion this is bad as you don't want heat from a pump bleeding into your loop and why I will always avoid the DDC.
Coolant, I swear by Mayhems X1 and won't use anything else. It has all the additives you need and comes in a wide choice of colours. It can also be used with most types of tubing.
Tubing is a personal choice. Flexible tubing is by far the easiest for a first timer and I prefer Mayhem 10/16mm clear tubing. It's cheap and it's good stuff. Hardline tubing looks better but it can seem daunting the first time you use it. Take your time planning it out and getting it right will reward you with a fantastic looking setup. The downside is that you need a few tools such as a heatgun, hacksaw, bending kit and fine sandpaper. The sandpaper is particularly important as you need to chamfer the ends of the tube before putting in the fittings so it doesn't tear the O-rings.
Fittings will depend on the type and size of tubing you choose. The size has to match the tubing exactly. Hardline fittings can only be used with hardline tubing and normal compression fittings can only be used for flaexible tubing. If going with hardline tubing it's probably a good idea to stick with the same brand for tubing and fittings to make sure that the sizes match up exactly. I have had tubing and fittings that were supposed to be the same size from different brands be a loose fit when put together. For hardline I get my tubing and fittings from a seller on Ebay called Mizucool. I use his own tubing which I believe is rebranded Barrow tubing and Barrow fittings which have four O-rings. For flexible tubing fittings I have found that much cheaper generic fittings are just as good as the expensive branded ones and I have never had any problems with them.
Most important of all is to do a lot of research. Read lots of reviews and find out all you can about each component of a loop and how good they are. Building a water loop is expensive so get it right the first time and you will have a good looking, well performing setup. Get it wrong and you will end up disheartened and wondering why you spent all that money. There are always people on here willing to help if you are stuck so don't be afraid to ask.