Okay so I am done now,
had to change for a different PICO PSU - ended up getting RGEEK 300W one from aliexpress, disassembled old Flex PSU and drilled a hole for 80mm fan from the front (cause of noise improvement) which I connected to mainboard since this way it won't keep spinning after I shut down PC what would happen if I used direct plugging to Mean Well unit. Gotten lucky and found AXP90x53 full copper for 17€ in auction so I used this one.
Stripped the extension cables from C14 plug and connected them directly to Mean Well unit.
Final build specs:
Intel core i5 13400F with Thermalright contact frame
Thermalright AXP90x53 FC
MSI B760I Gaming Edge
DDR4 Kingston Fury 32GB 3200MHz CL16
WD SN770 1TB
Gigabyte GTX 1650 4GB
Mean Well LOP-400-12 with RGEEK 300W 12V Pico PSU
LZmod a24 v5
Temps after 2h League of Legends run:
CPU max 65°C
MB max 57°C
GPU max 55°C hotspot 66°C
I might add 140mm fan in front of CPU fan or swap for 120mm CPU cooler fan to improve cooling of motherboard in future if necessary, atm I am happy with how it is, maybe gonna switch fan to Noctua A9x14mm for better acustics.
Below are some photos of the build.
