I’ve read not long ago, from a freeper who was working on the border, I assume BP, for years, that when NG help, usually they fill jobs that many BP do that are support roles, so that more BP can then take on the actual walking the line active jobs.
I have a cousin in BP and a son-in-law in NG. Also just this past Tuesday spoke with a State Senator on another topic and he brought up Texas NG going to the border. What you stated about the roles is accurate according to those sources up to now.
As I understand it now, in Texas anyway, roles could evolve to more NG action. NG will also be stepping up to do some patrols (after training for this) they can’t arrest illegals but will be able to detain and call BP for the legal work. That was my understanding from my senate conversation, any inaccuracy would be my fault because this was not my main topic of concern in the conversation so my recollection could be goofy.