Hello Friends,

Be advised this is a longer post, I am very curious and as you can see for yourself in a few moments, very serious about mining. I want to learn more, I want to follow through with this. So if you don't have anything productive to say, please do not waste your time with this post.
Now, I’m new to this so if there is anything at all that my ignorance is not allowing me to see, please shine some light on it.

For the past 3 months, I have been trying to research and investigate crypto mining and I feel comfortable enough to attempt to build my very own rig.
After many long hours, I finally want to begin thinking about purchasing a few key components. However, I ran into a few problems and I am hoping I can find some solution here.

Key Aspects of my build
1) I want to build a rig that is modular so that I can expand when I am financially available
2) I want to begin with two 3060ti GPUs

Problem 1
Power Supply
 
- How do you calculate the number of watts needed for your GPUs?  In my case, I want to power two GPUs that require a total of 400 watts. So then do I buy a 500w power supply to cover my needs running at 80% efficiency.
- When do want to add more GPUs? Would it be correct to assume that I need to purchase another 500w power supply to support another two 2060ti GPUs
And if I have understood this correctly, should I just buy a 1000w power supply in the first place?
- Question; Should I only trust 80 Plus certified power supplies or can I cheap out for a Chinese model.


Problem 2
Motherboards 

- I did have a hard time understanding motherboards. So instead of asking, I am just going to tell you what I know.
- There are five types of PCI slots x1, x4, x6, x8, and x16
- There are different transfer data rates. 2.0, 3.0, 4.0. The higher the better. My question with this topic is, does it actually matter purchasing a 3.0 vs a 4.0. I understand that there is a speed difference, but more so I am asking if there is a noticeable difference.
- Risers and splitters give you the option to have your GPUs connected elsewhere on your rig
- Those are the main parts that I understood, now some questions that I have
- Question; how do you find or calculate the maximum amount of GPUs that a given motherboard is capable of running efficiently?
- Question; is it best to buy a motherboard that has a set number of PCI-e slots and only use what is available? Or can I buy a motherboard that has, say 4 PCI-e slots, and use four splitters giving a total of 16 PCI-e slots that are available to use efficiently.

Problem 3
Hardware

Now that I am here I might as well triple check the hardware that I need in order to have a fully operating Mining Rig using NiceHash
- Some sort of frame
- Motherboard
- CPU that fits the motherboard
- CPU cooling fan? (optional? Or is it highly recommended)
- Nvidia GPU(s)
- Powersupply
- Risers
- Splitters (if this route is available)
- M.2 (i have no idea what this is or how many I need) (is this an SSD)
- RAM (also do know how much I need, will 2x 8GB, 16GB total be enough? They perform better if they are from the same manufacturer or can use different manufacturers)
- Storage (I’ve read I don't need a lot, so I'm guessing 500GB. Is it worthwhile to purchase a 1TB) 

For those who stuck around until the very end, thank you, I truly appreciate it. For those willing to hand out guidance, I will be eternally grateful and in your debt.