I would follow Peru Bob's advice, ETURK. I like to transcode straight away to ProRes LT and it's easy to edit with, no lag, no stutter. Your 4K HEVC at 10 bit and 60fps is too much to bear for your computer system. I don't even think an Intel processor with Quick Sync can help once you're into 10 bit territory. These formats are truly brutal formats and do need to be dealt with ahead of time....or else, well, you see what happens.