1. On topic........depends on where you live and the terrain you encounter. If you have lots of hills I cannot imagine it being the way to go versus just single speed. Single speed with freewheel is very simple and eliminates the problem of fixed gear trying to ride a track bike on the open roads and either 200rpm downhills or 10rpm uphills. Singlespeed you could at least gear for the hills and coast down in comfort with a front brake ready. If flat enough, it would be fine, but I would be annoyed quickly worrying about pedal strikes cornering a fixie. Mine is setup in my TT bike fit as a "pursuit bike" and I ride it on flattish country roads.
2. I do announce a pass on the open road to riders, and trails. If people are startled by a bell or voice for a pass, that's their problem. Most trail rules I've seen posted often include an "announce to pass" rule. Either way, regardless of whether the other person was speeding on trail, it's childish to race on shared use paths. Grow a pair and sign up for a crit, road race, track event, time trial, or something if you want to race people. Even a weeknight worlds ride. I'll never understand the impromptu Fred action of racing randos on trails.