Reasons for using multiple repos imho:
- Different retention policies for different content types
- Maybe you want to rsync repos only for certain content types somewhere else (cloud?)
- Possibility to later use separate locations or access permissions for different content types
Main reason for using a single repo imho: deduplication (if data chunks reappear across content types). This works extremely well and saves me a ton of space in nearly every repo I’ve ever created. As @kapitainsky said, restic doesn’t care about things like file number or size. No restrictions here until you get to a certain point.