Thank you for suggestions! No VPNs on my side, FFXIV got all needed exceptions in firewall and antivirus. Nothing loads at start so should be good too. As for using older dx version - dx9 seems to be working, but i won't call it enjoyable gaming experience.
Now to the good news. Scouting internet for solutions helped me to find A LOT of things to try i did that, no matter how stupid it sounded.
Just to recap things, clean windows 10 installation with fresh drivers on GPU, updated firmware for motherboard, updated chipset drivers and fresh clean ffxiv installation didn't help. Changing priority for ffxiv process in task manager and allocating only 6 CPUs to work with it didn't help as well.
So for ppl with AMD processor, not sure if there such function on intel ones, I don't really remember. But for AMD CPU's there is an option in bios for you called Cool&Quite - disable it. Let your CPU to work in normal mode or even aggressive one if you want. That option can undervolt your CPU when there is nothing heavy happening on PC.
Now for the fun part - pls don't laugh at me, i was really desperate there and was trying EVERYTHING. Found a suggestions that USB ports that you are using on your motherboard can play a role in crashes as well, i have no idea how and why. I have 5 usb devices attached to PC, so i changed ports and moved away from LAN port ( since on most of motherboards USB ports are near your LAN port ). After that i did DRS run this morning, not a single crash! So it worked! Hope it will help some ppl! (MAKE SURE TO UPDATE YOUR MOTHERBOARD FIRMWARE, ESP FOR AMD USERS)
And lastly i wanna add - yes, I found the solution, but that seems to be mostly problem of ffxiv code, that reacts so heavily on hardware operations (like overclocking or undeclocking) and even if you see dxerror or nvidia drivers error, it might not be actually GPU problem. It should be fixed by devs and i really hope it will be in upcoming patches (i don't have high hopes for small patches, but maybe for next expansion with graphic update? )
I hope my post will help ppl!