When used on a person, smooth transition to given move will be done.
The difference between playMove and playMoveNow is that playMove adds another move to the move queue, while playMoveNow replaces the whole move queue with new move (see Example 2).
A transition is only possible if the current and provided animation nodes are connected to each other in config (via connectTo/From and interpolateTo/From). The connection can be indirect (using intermediate animations)
For an immediate transition use switchMove. This command must be executed after mission start. If you place it into init.sqs / init.sqf or in the Init field of some unit, it will not work. Just add a little delay (~0.001) and then place the command.