So it turns out Blender can set multiple 'active'/locked viewport cameras simultaneously! Pretty useful for composing the scene while ensuring multiple viewpoints (possibly camera keyframes) look okay.

To set this up: - Tick "Local Camera" in the viewport's sidebar to the right, in the 'View' tab - With local camera active, choose a different camera from the options beside the local camera checkbox. This camera will only be specific to this viewport when you switch to camera view - Repeat for as many viewports as you wish! Just discovered it today! My life will never be the same 🥹