Loading

[Get Save Subsystem]
   ↓
[Load All Async]
   ↓
[Wait for completion]
   ↓
[OnComplete]
   ↓
   [Spawn player with loaded data]

void AMyGameMode::LoadGame()
{
    USaveSubsystem* SaveSubsystem = GetWorld()->GetSubsystem<USaveSubsystem>();

    SaveSubsystem->LoadAllAsync([this]()
    {
        // Load complete
        SpawnPlayerWithSavedData();
    });
}

void AMyGameMode::PostLogin(APlayerController* NewPlayer)
{
    Super::PostLogin(NewPlayer);

    // Get player's profile component
    AMyCharacter* Character = Cast<AMyCharacter>(NewPlayer->GetPawn());
    if (Character && Character->PlayerProfileComponent)
    {
        // Load saved data
        USaveSubsystem* SaveSubsystem = GetWorld()->GetSubsystem<USaveSubsystem>();

        FSaveRecord Record = SaveSubsystem->LoadRecord(
            Character->PlayerProfileComponent->GetSaveGuid(),
            Character->PlayerProfileComponent->GetSaveBucket()
        );

        if (Record.Bytes.Num() > 0)
        {
            // Apply saved data
            Character->PlayerProfileComponent->ApplySaveRecord(Record);
        }
        else
        {
            // New player, give starting items
            GiveStartingItems(Character);
        }
    }
}