I am on a AR project (with Unity3D and ARCore) in which we are having a very huge area to track. For that we first developed a demo application which worked very well. Then later started developing in large area (600 meter * 600 meter) and a polygon count of 30M triangles. When I built the application all the assets in the scene became very tiny, real time scaling objects are turned to toy size. The same application in VR went very well.
I wanted to know are there any polygon count or area limitations in AR? If so is there any option to create a miniature area with ant camera.
There is no strict limitation on the number of polygons in any AR scene. However, as a general rule, a seasoned developer will not create AR app containing more than 100K polygons. This is true for any modern framework, be it ARCore, ARKit, Vuforia, RealityKit, or MRTK. 30M polygons is unacceptable amount for robust AR app. Your AR app not only renders 3D geometry with textures and animation but also must track a real world environment and anchors at 60 fps. It's quite heavy burden.
Read Optimize Model Geometry and Transparency section in Apple's article.