the tonal quality will be from the material of the cap and the different capacitance value.
the voltage rating is meant for the safe working range where the cap can be used in a system that is installed.
For guitar, we are only seeing voltage in the milivolt range. Super tiny amount, when you compared it to the voltage rating of those orange drop caps.
The bigger the value, usually just mean the physical size of the cap will be bigger, thus taking up more space within our geetar cavity.
You should be more concern with the material of the cap plus the capacitance value then the voltage rating. Hehe for a cap with 400v rating, you can prolly use it in tube amp or something much more bigger that draw power directly from power point etc.
For guitar usage, its overkill for the voltage rating(kinda like using a swimming pool, to put fresh water for drinking, for one household with 4 people..). But in term of the material of the cap and its capacitance, thats where it has a bigger effect for the context of usage in geetaring.