It is enough Corsair HX1200 Platinum psu for 4 1080 ti?
It depends on the algo you mine and overclocking settings, for example equihash, ethhash has stable power usage but skunkhash, timetravel algos have enough unbalanced load, so 1080 ti can consume up to 300W, so HX1200 is next to one, but for downvolted cards it could be enough
That is good enough almost every algo I did I run my 1080ti power limit 80% or less for long term usage. Skunkhash isn't too bad when you drop it at 80%. Im still near 52-47 mh/s
Most PSU are near the 1200w rating with the 12v rail. You keep the load under 80% that gives you 960w. If you have higher TDP models of the 1080ti 74% power limit is good for 24/7. It leaves 131w for 52w Celeron CPU, RAM, 4 fans, motherboard and SSD. As for fans I use 4 140mm high speed yate loon fans. It's been a fan of choice since 2008. Only consumes 8.4w each.