Effects that select units based on stats, such as Chill Def/Res 3, directly select the unit with the appropriate stat(s); they do not compare the team's units pairwise to decide which unit has the highest or lowest stat(s).
Effects that check if a unit could make follow-up by decreasing the Spd difference, such as Potent 4, are not affected by Phantom Spd.
Effects that alter the Spd difference, such as Frozen, are not affected by Phantom Spd.
Phantom Spd stacks with other effects that treats a unit's Spd as if granted by a certain amount.
For example, if both Buffer 4 and Phantom Spd 3's effects trigger the unit with both skills will have their Spd treated as if granted +17.
Chill Def/Res 3, directly select the unit with the appropriate stat(s); they do not compare the team's units pairwise to decide which unit has the highest or lowest stat(s).
