I have reached over 100% of the threshold and would like to use my computer for other tasks, will I still receive the payment without any active workers?
You will recieve a payout if you are above .1 ETH, reguardless of active miners. Unless of course your account gets locked or something of that nature.
It is safe to change after you get to the .1 ETH limit. Do stop mining before you see .1 ETH, but after your fine.