Upgrading DVR

I currently have a nearly 4 year old X1 box.  I have a Samsung 4k UHD HDR TV.  I am subscribed to the Blast 200Mb service, which is the highest speed available in my area.  I am thinking of upgrading to the latest box, the XG1v4.  From what I have read, there are two versions of this box, the XG1v4 and the XG1v4a.  What are the differences between these two boxes?  Do either one of them have an internal HDD for storage?  I also noticed that there is a USB3 port on the back...can that be used with an external HDD for storage?

I have my own modem and router; the modem is an Arris Surfboard 8200, and the router is a Netgear R9000.  Will I have any compatibility issues with this hardware? 

Lastly; if I do decide to upgrade, can I specify which of the two boxes I want?  I ask because I have read that the 'a' version uses an RF remote, while the non A uses an IR remote.  This really doesn't matter much, but I wanted to confirm that is the case. 

Thanks!