when I checked my wallet before 250k moved itself from Spendable to Stake. After restarting everything is back in spendable. Is there a difference in mining speed whether it's in Spendable or Stake?
no, there is no difference in speed. your reward is dependant on how many coins you own, and how much of it is matured/staking.
you can reserve how much you spend and how much to stake. Read FAQ.
a block was found during the time you closed your wallet and opened it, so that's why your coins were spendable again.