Probably. Pro will try to max out your connection unless you tell it not to (Modify > Expert > Cloud > Advanced > bottom option) and/or reduce the number of threads (same page, further up). See the contextual Help on that Advanced page (press F1) for more background, including the fact any bandwidth reduction will be in 'burst mode'
Bear in mind whatever else you're trying to do will be contending with the profile. You might want to consider scheduling your backups for 'down-time' (e.g, lunch)
Bear in mind also that - as clearly stated in the Help - using Versioning with Fast Backup will require the profile to scan S3 for remote Version housekeeping anyway, thus neatly negating most of the benefit of Fast Backup anyway. Version info is not stored locally, but enumerated 'on the fly'
Bear in mind whatever else you're trying to do will be contending with the profile. You might want to consider scheduling your backups for 'down-time' (e.g, lunch)
Bear in mind also that - as clearly stated in the Help - using Versioning with Fast Backup will require the profile to scan S3 for remote Version housekeeping anyway, thus neatly negating most of the benefit of Fast Backup anyway. Version info is not stored locally, but enumerated 'on the fly'