Usually this is social rather than competitive so local conventions can apply. However blitz is used as a tie break in knock-out events - the structure is that one player is given more time than the other but the rule is that the player with less time will win the tie break in the event of a draw.
So what should happen if the position comes down to K+N v K+N as in the recent women's world championship and one player runs out of time. The relevant article in the rules of chess is
9.6
The game is drawn when a position is reached from which a checkmate cannot occur by any possible series of legal moves, even with the most unskilled play. This immediately ends the game, provided that the move producing this position was legal.
In the recent event the term even with most unskilled play was interpreted to mean that a win with K+N with K+N was possible because a helpmate could be constructed.
I suppose my point is that players need to know how these totally drawn (but not legally drawn) positions will be handled before they can assess whether the time odds are fair in these shoot-outs.