It is not possible to deploy either Operational-Best-Practices-for-FedRAMP-HighPart1.yaml or Operational-Best-Practices-for-FedRAMP-HighPart2.yaml as StackSets due to at least these following rules which are found in Part2 and Part1:
AcmCertificateExpirationCheck
ApiGwCacheEnabledAndEncrypted
ApiGwExecutionLoggingEnabled
ApiGwSslEnabled
AuroraResourcesProtectedByBackupPlan
AutoscalingLaunchConfigPublicIpDisabled
BackupPlanMinFrequencyAndMinRetentionCheck
CloudTrailCloudWatchLogsEnabled
CloudTrailEnabled
CloudTrailEncryptionEnabled
CloudTrailLogFileValidationEnabled
CloudtrailS3DataeventsEnabled
CloudwatchAlarmActionCheck
CloudwatchLogGroupEncrypted
DbInstanceBackupEnabled
DynamodbAutoscalingEnabled
DynamodbInBackupPlan
DynamodbPitrEnabled
DynamodbResourcesProtectedByBackupPlan
It is not clear why these rules need to be present in both packs.