A fair question, thank you for asking. Yes, positioning is very important in fighting games and so too here. First, I should address that the vibe system has no mechanic equivalent to an attack of opportunity like in d20. If a target passes with range of an attack or withdraws there are no free attacks. (Say for in Beneath Twisted Earth which features the Overwatch action, or arguably if the GM wishes to use the Delay action to set up a conditional trigger similar to d20.) Otherwise the only way to gain attacks not on your turn is to use a Reaction such as Parry or Collateral Attack.
As for maintaining your desired distance when you can move, but your opponent can move on there turn, players in Festival of Fighters would be encouraged to pay close attention to their Stances' Effective Range and the traits they gain from Archetype Levels during Fighting Style Construction. Many of these traits grant free moves or improved movement when certain conditions are met. For example, it a fighter with the Level 1 of Zoner Archetype moves away from their designated target, their Movement Rate increases by one, allowing them to quickly with draw to a preferred distance. Similar traits can be found under different conditions. The use of these archetype traits can assist with a fighter's positioning during combat.
If your question was concerned with the more basic leve of movement, a large part of it depends on the combatant's movement rate. A combatant who is slow is unlikely to be able to control their positioning well without help from allies or abilities, while fast opponents may race across the battlefield after one another. Clever play would certainly be encouraged under these scenarios to use your traits or ability to hinder your opponents movement.
Did this satisfactorily answer your question, or was there something specific you wanted to dig into?