What’s the best monitor to pair with my LG 48CX and how should I orient them in a 6.5 ft niche?

I’m setting up my new office and trying to figure out which monitor pairs best with my LG 48CX and how to arrange them ergonomically.

The 48CX has been my main display (It has been great), but I’m buying a new high-end monitor to become the primary screen. I care more about picture quality and aesthetics than extreme refresh rates — I mainly do gaming (not competitive shooters) and general productivity. Budget is flexible

Setup details:

• Niche where the monitors go: 6.5 ft wide
• Full wall with countertop desk: 12 ft wide
• Sitting distance: around 4–5 ft
• Wall will be finished with black acoustic slat panels (photo below)
• IT company will handle wiring; I just need to lock down monitor size, placement, and mounting height before they start
• I’ve even considered mounting the LG vertically (portrait) to save space, but not sure if that’s practical long-term

Looking for advice on:

• What monitor (size/model) pairs best with the 48CX for this distance and space
• Whether a stacked, side-by-side, or portrait setup makes the most sense

The Niche

The Panels Im planning on using