Holster mount for Run & Gun?

[DukeSoprano]

My indoor range has a Run & Gun every Thursday night. It is not affiliated with any of the sanctions.

I took an introduction class last weekend at the outdoor range I belong to and enjoyed it.

The gun I want to use is my full size Wilson Combat 9mm X-tac
I would like to add a mag well soon.

The Holster I plan to order is a leather lined Garret Industries:
http://www.giholsters.com/product-p/pack1001.htm

The Belt I plan to order is a Shooters Connection:
https://www.shootersconnectionstore.com/Shooters-Connection-Ultimate-Competition-Belt--P4644.aspx

I am a little confused by all the different holster mounts Garret offers:

Any advise would be appreciated! I am a firm believer in buy once cry once.

Thank you,
Jeffrey