For what it’s worth I run;
Road; 48/16 (I don’t skid that one!) (79 inches)
Commuter; 42/16 (69 inches)
Shhh Tracklocross; 42/20 (57 inches)
MTB; 34/21 (43 inches)
All these are chosen very scientifically, what I had kicking around at the time, they then just stayed.
42/17 is 67”, I tend to run 46/19 or 66”on my everyday fixed which has guards, dynamo, flat bar, 35mm tyres etc.
On my purer ‘road’ fixed I run 48/19 or just shy of 70”.
My gear is usually the lowest of the group I ride with but I can spin the highest cadence so I’m able to keep up on the descents.