When I played (past tense, not recently) in serious comps with a partner, I used to discuss club selection.
I remember one incident when we (it was my shot after his drive) decided it was 185-190 to the pin. I wanted to go with a 3i (to take out the front bunkers) and he asked me to hit a 4i at the left bunker, hoping to see the ball kick right onto the front portion. It came off a beauty (it was the first hole and SI 1) and he holed a 6 footer for birdie nett eagle start. From then on, I always double checked with him.....

I don't believe I would ever ask an opponent, even if it was allowable.

As for judging distances by eye....I don't do it....unless I have to. If I'm past the 150/200 I pace it out, if I'm short I add on whatever I think it is. Around mine, there are very few useful distances on the stroke saver, but on some courses, a detailed stroke saver is brilliant. At some courses (Little Aston springs to mind) you need full info for lay-ups as well. Some holes have bunkers everywhere and it can be quite taxing doing the maths.