while mining...
1. how much power does an optimized system with one 1080 ti roughly consume?
2. how much would a whole setup with x4 1080 ti´s consume?
3. how accurate is whattomine with its numbers?
1 and 2 vary based on system configuration and what constitutes "optimized" in your mind (efficiency, raw hashrate, etc.), as 2stout mentioned.
3.) Whattomine is fairly accurate, but not necessarily useful.
The preset hashrate and power information is generally way off, and will definitely be unable to account for individual rig settings.
The information about each coin's network hashrate --> block difficulty should be kept up-to-date, save for the case of delays or sharp changes mentioned by lathrodectus.
However, price information is a little trickier. The rates described by Whattomine are generally not the same as what you'd end up getting after actually exchanging them, but it's difficult to say if this necessarily impacts certain coins more so than others. (I.e. if all coins are over/underestimated in value to the same extent, then the ranking in terms of fiat revenue or profit remains unaffected.)
As far as its usefulness goes, do note that the top coin to mine for a given system configuration will rarely remain so for more than a few hours, and it's difficult to say whether this is primarily caused by a price drop, mining difficulty increases, or a combination of both.
(Suppose you had done the necessary setup to mine every coin listed on Whattomine, and check for the most profitable coin every minute, 24/7. Mine the most profitable coin for a few hours, and then notice it's no longer the most profitable listing. At that point, if you sell your coins that you are holding, did you obtain the fiat equivalent of what you were led to expect? If the loss of the "most profitable" title fell purely due to a mining difficulty increase, then you would be fine switching your miner off to the new "most profitable" option, and then selling the coins you had previously mined. However, if the profitability loss occurred purely due to a price drop (depending on magnitude), then the past few hours you spent chasing the "best" shitcoin just went to waste, in terms of the short-term result.)
In short, Whattomine will not account for the speculative aspect of mining, which is an important part that cannot be ignored. (What and when to hold, what and when to sell, etc.) Overall, very few miners wish to hold miniscule amounts of tons of shitcoins, hence many users that want profit-switching capabilities flock to services (such as NiceHash) that offer payouts in the cryptocurrency of their choice.
