I think it would matter very little. For short fasts cutting carbs has a bigger impact because you have a smaller window to try and accomplish things; for a long fast it would impact things a lot less.
Works best if you start your fast after dinner. That way you sleep through the insulin spike.
If you consume high carb food before attempting to fast you’ll be miserable. Your blood sugar will spike and crash and it will take a lot longer to get into ketosis.
Its highly recommend you eat low carb before fasting to stave off the effects.