The reason to cut the outside 1st is twofold.
1) The mower was always on the right side and since the outer windrow takes longer to dry it went first.
2) This also gave you room to turn around straddle the 1st windrow and continue cutting on the right.
As far as how tight the turns can be it depends on the machinery and field size, if the UJ chatters it's too tight.
For speed it depends on equipment, sickle-mower is the slowest, discbine the fastest, actual speed is a combination
of which cutter & tractor hp you have, should try to maintain an even flow to avoid clumps.