The Exynos 9825 has the same Cheetah M4 cores and Mali-G76 GPU as the 9820, but Samsung hasn't listed the die size or certain key processor CPU and GPU speeds. It did say, however, that the GPU would run at a higher clock speed, so it will outperform its predecessor, especially for mobile gaming.
Other features on the chip are a 4G LTE modem that tops out at 2Gbps and Samsung's "neural processing unit" that will power AI photography and augmented reality features. 5G is not built into the processor, so Samsung will likely use its Exynos Modem 5100 for 5G variants of the Note 10.
Samsung's Exynos 9820, featured mainly in Korean variants of the Galaxy S10, was considerably larger and less power efficient than the Qualcomm Snapdragon 855 chip powering US Galaxy S10 models. That's likely because the Exynos 9820 was built using Samsung's 8-nanometer LPP tech, while the Snapdragon 855 was manufactured using TSMC's 7-nanometer, non-EUV process.
Now, Samsung has likely narrowed that gap, though again, it didn't say by how much. The company might be saving the news for the Galaxy Note 10 launch, though at this point, it seems likely that US versions will feature the Snapdragon 855 processor, as usual.