13.5 MH at 60 degrees is a very good mining result.
My video cards do not want to mine more than 10 MH, and any increase in frequencies leads to a reboot of the farm.
You can use more powerful fans to cool your graphics cards to lower temperatures, but I wouldn't do that because you already have a great hashrate.

Congratulations on your progress.
The Asus company congratulates you on the fact that you are deprived of the official warranty for the video card
On RTX3080 video cards, only Palit Gaming is perfectly mineable without replacing thermal pads.
Your thermal pad manufacturer has a good Thermalright TF8 that is better than the MX-4.
https://aliexpress.ru/item/33010425469.html

You won't have any driver or hardware compatibility issues.
But you can't avoid other overheating problems, because the RTX 3090 and 2080 TI are the hottest cards
The 3060 should be inserted into the (x8) slot so that there are no problems with decreasing the hash rate, and in your case it is better to install at least one video card through the raiser to achieve better cooling.
Even if you install both video cards in (x1) slots, it will not affect their mining hashrate.

The main mining expense is paying electricity bills.
Other expenses are rent (if you don't use your premises) and security.
When we talk about investments, we must know your capabilities and investment amounts.
For example, you can figure out which is better if you buy $ 20,000 worth of cryptocurrency now or buy video cards for mining in your garage and mine for 3 years.
The cost of electricity is, for example, 6 cents per kilowatt.

If you bought Ethereum for $ 150 more than a year ago, you would already have made a lot more than miners.

Ethereum is not a solo mining coin.
You may not find a block for several years, and most likely you will.
But in a week you will be tired of it.
Better join a mining pool and get permanent mining rewards.
I would not go to mine Ethereum classic in solo mode with such a hash

Without the compute mode, your hashrate would not rise above 15 megahashes.
I can suggest you to use the original bios, and try different settings -strap 1 -strap 2 -strap 3
5- most aggressive

But from my own experience, I will say that not all RX580 video cards show 30-31 MH. 28 MH is also a good result

https://www.techpowerup.com/vgabios/192936/sapphire-rx470-8192-161220
This BIOS has the following memory types
8192 MB, GDDR5, Autodetect
8192 MB, GDDR5, Samsung K4G80325FB
8192 MB, GDDR5, Micron MT51J256M32HF
I would not flash a video card with a BIOS that lacks support for the required memory.
Try to write to the official technical support. Write that the card is not under warranty, but you bought it from a miner and want to use it for games.
Or install atikmdag-patcher.

This company is not a scam.
Where was your mind when you thought they would sell you an ASIC that earns $ 270 per day for $ 23,000?
Thinking about a new sportcar?
You have not checked this information, have not asked for advice on the forum.
And after they lost money, they began to blame the Linzhi company for this.

Probably you have a Samsung memory, because only it allows you to underestimate the values so much.
Typically Core Undervolt is chosen from the 700-800 range, but you're in luck.
I have no other suggestions for setting up a video card. If problems arise in the future, then Core Undervolt will have to be increased to 700

If your video card consumes no more than 150 watts, I would use these adapters.
Of course, I would check the thickness of the wires and the build quality.
If video cards with high consumption are used, then I would use other power supplies and try not to use adapters.
I assume that 1 branch of the power supply unit has a safe load of no more than 150 watts

VDDC/VDDCI  750
MVDD don't install
The default for Navi is 1350 mV.
If there is not enough memory voltage, then the problem will disappear.
I have not configured MVDD on my farm.
You may have problems due to BIOS modifications, so miners advise you to test video cards without mods for several days

You are already the second user who cannot use open rig.
Use special cases for mining farms

Each old computer will additionally consume 70-100 watts, so 4 computers will additionally consume 350-400 watts of electricity.
Your farm does not need a 1000 watt power supply, an 800 watt power supply is sufficient

If you cannot use an open installation of video cards, then buy a case like this.
The case can be equipped with raisers.

In this case, you do not need to pay dearly for a special fee.
An inexpensive pre-owned ASUS 970 PRO GAMING motherboard is suitable for a fascinating assembly.

Any information leak from such companies is a planned action in order to pass fake information to competitors or to do it on purpose in order to get profit.
Now Nvidia will tell gamers that the company did everything it could, but bad hackers ruined all plans.
After such events, I would not believe this company. Amd do not create problems for miners.

Now you can buy prepaid asic from official sellers in 6 months.
The most reliable seller is the one from whom you can check the ASIC on the spot and pay money.
Do not settle for prepayment when buying ASICs from unknown sellers.
And it is probably safer to buy video cards in stores in your city.

I didn't know that such equipment existed.
But the habit of assembling farms on ordinary motherboards is very difficult to overcome.
In the event of a breakdown, the motherboard is usually damaged. The processor and memory remain working. And the motherboard has a 36 month warranty and it is possible to extend the warranty to 60 months.

But I would like to read the instructions for setting up this equipment with Hive OS.

Why remember 2017 if the author of the topic is talking about today's results.
Mining on processors is difficult to make profitable, because each processor needs a motherboard, memory, power supply, etc.
If you have a computer with a good processor, then you yourself must decide whether you need to use your computer to earn 10-20 dollars a month.

There is a mode in MSI Afterburner settings: "extend the official overclocking limits"
I do not remember the exact name, but I think you will find this setting.
Why overestimate hardware frequencies to get a small increase in hash rate of 2 megahash?
This will lead to faster damage to the laptop due to overheating.

Update your drivers if you have them before September 2020.
Install  MSI afterburner

Core Clock 1100 MHz
Memory Clock 2000 MHz
Power Limit  90
These are the basic settings for the modified BIOS. (Mod with 1750 over 2000 straps)

If you do not modify the BIOS, then you can use this mode in the miner
-strap 1 -rxboost 75
These values need to be selected individually for your card.
I do not know what kind of memory your video card has

https://rvn.2miners.com/help

Settings for NBMiner:

Settings for TeamRedMiner:

I had problems like this and it is not a miner settings issue.
Download the latest version of the miner
https://github.com/todxx/teamredminer/releases

Connect with any other pool, try 2miners.com and beepool.org
https://miningpoolstats.stream/ravencoin
After changing the pool, this problem was solved for me.