Library / Develop colour profile changes - New Dell 4k Monitor

So I've been scouring the interwebs trying to figure this out. I've just got a new Dell U2723QE UltraSharp 4k monitor. I'm sticking to the monitor's hardware sRGB internal setting as the foundation. I've set the ICC profile as such within my windows OS Colour Management to match the monitor model. 

So with Lightroom, changing between the Library and Develop modules seemingly changes the white balance colour of the images. If I turn GPU processing off, it stops changing. It upholds an overly blue toned image colour across broth Library and Develop. Turning GPU processing on, the Develop module displays the image matching near perfect to the back of my Canon R5, straight out of camera look, so I'm inclined to see that as the most accurate. But Library view sticks to the blueish tone image. 

Setting 'Photoshop > Colour Settings > Working Spaces > RGB' to 'Monitor RGB' (matching OS Colour Management selection) seemingly gives me accurate white. But that colour profile doesn't work when bringing external edits in from Lightroom which wants to work with ProPhotoRGB, which is what I've always done and want to keep for colour accuraacy with my client's work, etc. Making the Photoshop Color Setting ProPhotoRGB though gives my images the blueish tone as I see it in Lightroom's Library module. When I'm in Develop with my accurate colour and the GPU processing on, the filmstrip thumbnails down the bottom are still with the blue tone. 

To top it off, if I drag Lightroom or Photoshop across to my second monitor, my older HD Dell U2415, the problem doesn't exist. I can actually see the blue tone stay on screen for a second before it transitions! So it's clearly a colour profile communication issue directly related to this new 4k monitor. Is it a monitor setting or a software setting in this case? I've got no idea.