If you do decide to rent NiceHash power by the way it's probably better given to a smaller pool as you end up with a much bigger cut of the block reward.
does this mean your "luck" is higher with a smaller pool compared to stable "smaller" payouts from supernova for example?
hashing with 7 1080tis
more like "luck plays a higher part"; if your rented hash finds a good amount of blocks then you'll end up with a big cut of it on a smaller pool, otherwise on a larger pool you might not find as many blocks but still get a reasonable payout.
i.e. if a pool is 'lucky' then the benefit of that luck goes to the people contributing the most hash, on a huge pool where you are just 1% of the hash power if there is a luck streak then you won't benefit as much as if you're 20% of the hash on a smaller pool
in the end it evens out - as long as you're on a pool with enough hash to find blocks regularly you'll end up with roughly the same amount of coins for the hash