Order Of Data Load And Index Creation / Move Indexes To Separate Filegroup?

We are running SQL Server 2014 Enterprise Edition (64-Bit) on Windows 2012 R2 Standard (64-Bit).

1. When to create indexes, before or after data is added? Please address Clustered and Non-Clustered Indexes.

2. To move indexes to it's own filegroup, is it best to create the NON-Clustered Indexes on the separate filegroup with code similar to the example below?

CREATE NONCLUSTERED INDEX IX_Employee_OrganizationLevel_OrganizationNode
ON HumanResources.Employee (OrganizationLevel, OrganizationNode)
WITH (DROP_EXISTING = ON)
ON TransactionsFG1;
GO

I have read the following links that states that if you create the Clustered Index on a separate filegroup, it would also move the base table to that particular filegroup. (So I take it that you ONLY can move NON-CLustered Indexes to a separate filegroup.)

Placing Indexes on Filegroups:

[URL]

By default, indexes are stored in the same filegroup as the base table on which the index is created. A nonpartitioned clustered index and the base table always reside in the same filegroup. However, you can do the following:

• Create nonclustered indexes on a filegroup other than the filegroup of the base table.

Move an Existing Index to a Different Filegroup:

[URL]

Limitations and Restrictions

• If a table has a clustered index, moving the clustered index to a new filegroup moves the table to that filegroup.

• You cannot move indexes created using a UNIQUE or PRIMARY KEY constraint using Management Studio. To move these indexes use the CREATE INDEX statement with the (DROP_EXISTING=ON) option in Transact-SQL.