The cushion is firm and preety comfortable. It's not gonna sink so easily, typically soft cushions tend to sink overtime.
Usage marks will be there but it's quite easy to clean it off and keep it shining. The breathable fabrics and the mesh netting does accumulate dust overtime. I just use a blower every 3 months or so to blow it all off. Didn't require any wet vacuum cleaning so far.
My height is 5'9 and there is enough room to adjust the height lever and I can barely touch the headrest with full height. So 6'1 should work fine.