Introducing and Questions from a Newbie

[_NoXx_]

Hello Bitcointalk Community,
in the first place, I am happy to have discovered such a community. After a short read it was immediately clear that everyone here takes the other seriously and respected.
The quality of the posts and answers stands out, which is why I decided to start here as a beginner.

Short word to me:

A young motivated media informatics student who has been working for Bitcoin, Mining and co. For several years. Interested,
However, thanks to financial resources never had the opportunity to engage more deeply.

The Black Friday was used and ordered:

               Product number

graphics Cards
    SAPPHIRE Radeon RX 580 NITRO +, graphics card x3
    FX Radeon RX 580 GTS Core Active x2
    Gainward GeForce GTX 1070 Phoenix x1
    Palit GeForce GTX 1080 Super Jetstream x1

Mainboard
    Asrock H81 PRO BTC R2.0 x2

CPUs
    Intel Celeron processor G3900 x2

CPU cooler
    Alpenföhn Brocken 2 1
    be quiet! Dark Rock 3, CPU cooler x1

power Supplies
    Corsair HXi Series HX1200i - 1200 Watt 80 Plus® Platinum x2

Fan
    Cooler Master MasterFan Pro 140, case fan x2
    Cooler Master MasterFan Pro 120 2
    Aerocool P7-F12 Pro RGB 3 Series, Case Fan x2

Storage
   Apacer AS350 120 GB, Solid State Drive x1
   USB stick 32GB x1

R.A.M.
   Ballistix Sport 8GB Kit x2

Others
   YIKESHU PCIe PCI-E 16x 8x 4x 1x Powered Riser x2
    AOMAO Desktop PC Computer On and Off Switch x2

Opinion:

Why everything was ordered twice and not reduced to a miner?
Quite simply for two reasons.
1. A matching power supply to power all GPUs is too expensive.
2. In the future prefer two miners to equip / expand with more GPUs.

If you have not had the desire to stop, continue reading to my questions:

Hardware:

Was something forgotten?
How do the GPUs work together and are they compatible at all?
CPU and power supply sufficient?
Is it even profitable to mine with this hardware?

Software:

Which OS best use?
Which miners use eg NiceHash Miner?
How useful is a custom BIOS? If YES, a matching link is welcome (if allowed).
What settings to keep fans and GPUs running as long as possible?

General questions :

Which COIN is currently the most effective at mining with this hardware?
Recommendations to a public or private pool?
Difficult question but maybe even suitable overclocking / undervoltage settings for maximum hashrates?
What tips and tricks would you have for a beginner?
What has caused you problems in the past, what should you pay attention to?
The miners were scheduled to set up on the balcony weatherproof.

   How dangerous can it be for the hardware?

    Could cold be dangerous below 0 ° C?

Finally to the final word:

I hope I did not scare you too much with all the questions, besides, I know that much is already on the net.
I've also read, but much outdated and not hardware concretized.
I'm happy about every answer, even if she does not answer every question.
Every criticism, every suggestion for improvement and every opinion is welcome.

Beginners NoXx

[wacko]

The cards you bought are all good (except maybe the XFX with its quite mediocre cooler). The PSUs are good. Yes, these cards can all work in one rig just fine. Any OS will do for mining, but you'll need to mod your AMD cards first and that's easier to do with windows than with linux. Nicehash miner is fine.

I've also read, but much outdated and not hardware concretized.

Learn to do research, there's hundreds of topics just like yours here, on this forum, and no, most of them are very recent (due to the increase in mining profitability this summer) so the info there is all still relevant.