What exactly are you interested in learning from this experiment? Q. How many polygons can you push in if you use just models? A. Right around 850 000 polygons, modern GPU doesn't really cares about the polygons, it's doesn't matters if it's 5k or 30k, it will render it quickly. Special effects and post processing are the ones that will cause FPS drops. Best example is bloom in UrT HD. As soon as i turn it on, my GPU starts working 100%.
Q. How big textures can you use and if it's better to use one big instead of several smaller textures? A. 2048 is about as high as you can go. I would love to see support for 4k textures. Simply cause it's easier to create a decent terrain texture when you work with an image that can cover a super large surface. And if you for example have a lot of smaller models you can place all their skins into one texture. So all your foliage for a map could fit into just one image.
In UrT 4.1 i can't see any difference at all in changing the texture detail level. Those textures are just too small to affect performance. You'd have to be using a prehistoric ati 9800 128 MB GPU to notice an improvement in framerate. Since an average 512/1GB GPU can be bought for pocket change today there's no real reason to worry over texture size, not when your top limit is 2048, recommended size 1024 and best way to go is 512/1024 and use lots of decals to add details.