Others have said it and I must agree ... Get a D5 or one of the variants if you really feel the need for the bells and whistles.

Whether you get a ut60 rad or an XT45 won't make a huge difference to the temps you will run at and the thinner rad just might allow you to run quieter if you so wish.

I ran Delta fans for 2 years and agree they are great but even undervolted, the faster ones, those in the 3-4k rpm range, are not for everyone from a noise or tone point of view.... but hey, fans are an easy and possibly fairly cheap change to make later if you wish. I now use 2150rpm GT's but have only just about run them for a year so I cannot say they last for ages yet.

If you are a bit limited for space in that case then maybe consider one of the EK combined pump top and tube res arrangements or the bay res equivalent.

10mm/ 3/8" id tube will be fine.

cpu and gpu blocks are likely much the same in performance if you stick with the better makes in my view. I have some favorites as I am sure others do too.

So, are these parts going to give you the absolute best watercooling around? Probably not. for that you may need 2 pumps and a rad like a Mo-ra or phobya Nova then maybe sensors and $300 worth of controller but then that is beyond your current needs. My recommends above will not disappoint I am sure

Some have said that you need to strip and clean all this gear often. I am not going to agree with that, but then most here would not agree with my solution to this potential problem

To give you the best possible advice the folks here need details: Details like what ambient temperatures you will have to deal with and they will want to know your budget. If it is too low then custom water is not a reasonable choice this time. If on the other hand the sky is the limit, the knowledge is still here on these forums. If you are willing to listen most of us will be able to justify any recommend we make.

It sounds like small steps and chunks of info suit you best so take it one or two items at a time from the list:

pump, block, block, rad, res, tubes, fittings, fans, ....Sensors? Meters?