R6400v2 bridge or access point or vlan

> [...] In our RV we have a wi-fi gateway for controlling the slides,
> lights, etc. [...]

   That tells me nothing about what it is, to what it's connected, or
how, or how it's used.  Maker?  Model number? Any useful information at
all?

> [...] This unit is seperate from any internet connection. [...]

   But the R6400v2 has some kind of Internet connection?  Any clues on
that?

> [...] The unit in the RV also has a static IP of 192.168.1.1 (can't be
> changed) and needs to see the router at 192.168.1.2. [...]

   If you say so, then I'm willing to pretend, but I've never seen a
device whose IP parameters "can't be changed".

> [...] I have setup my AC1750 R6400v2 to be able to do that. [...]

   How, exactly?

> [...] how can I connect to the campground wifi signal through the
> R6400v2 at the same time? [...]

   What should I already know about your "the campground wifi signal"?

> [...] Would this be setup as an access point, bridge, or vlan? Or some
> other way with other hardware?

   I don't know enough about what you're doing with what, or how any of
it connects to anything, to make a guess.