According to the answer on Why do shields in Star Trek "wear out"? the TNG technical manual says the Defense Shields are basically form fitting. And this aligns with what I remember of TOS, mainly the hacking scene from Wrath of Kahn, with the lights on the shield display fitting around the ship display.
But in TNG and forward, I remember the shields being very bubble like, especially during phaser strikes. Is there any out of universe explication for the difference? Any in universe changes to shield tech or explication?