is it safe to connect 1080ti thru one cable using spliiter so one cable connects two pcie on card when using 65% power settings
You mean like this
I've been powering my 1080ti's like that for 6 months now without a problem. Cables don't even get a little hot even at 75% TDP.
I thought it was unsafe to do this for video cards drawing more than 200W?
that depends more on the quality of cable. good quality 16awg wiring can handle 300W+, while lower quality power supplies may get hot wires above 200W. at 75% tdp the card should draw less than 200w