Not safe at all, most auto clickers use extremely robotic movements/clicks and therefore easily detected. I don't think they do resets anymore, haven't heard of any recently, they just give a 2 day ban, and then a perm for 2nd offense.
Personally used autoclicker for 99 mage on over 4 accounts and no resets or anything have come to me. Majority of the time I was still active in the runescape chat. or was at least aware of what was going on, just incase.
Yet sometimes I would let it run a good 5 hours without me even there and it was fine. I also haven't acctually heard of people getting banned for it
Real knowledge is to know the extent of one's ignorance.