Reminder of the current known specs for the T239:
The GPU is actually a bit of Ampere, and a bit of Ada Lovelace, using Ampere Silicon and Optical Flow Acceleration, but using Ada back ports of NvEnc and Clock Gating. Additionally, there is a File Decompression Engine embedded in the SOC, along with 4 PCI Express Controllers and up to HDMI 2.1-Level video output bandwidth. All of this has been confirmed by the NVIDIA leak.
Shipping data, meanwhile, has confirmed that we will be getting 12GB of LPDDR5X running at 7600 MT/s, which, when paired with the 128-bit bandwidth, should mean up to 121.6GB/s when docked, which is an 18% uplift in memory bandwidth from the previously speculated 6400 MT/s speeds, that otherwise would have resulted in 102.4GB/s in max memory bandwidth. Know that handheld mode will likely underclock the RAM in order to prioritize battery life.
One current concern, per Digital Foundry, is that 48 Tensor cores may not be enough for some games to upscale to 4K without some compromises. Meaning that we probably should not be expecting 4K @ 60FPS in most games, and some games may not look particularly great in terms of fidelity when DLSS is trying to upscale to such a resolution, as they may be trying to upscale from as low as 720p. Additionally, a "source" had reached out to Digital Foundry, and confirmed with them that there is no Deep Learning Accelerator in the T239, so DLSS won't have any kind of accelerator to boost its capabilities. Therefore, temper your expectations for now, but know that 1080p should still look pretty clean for the most part, and visual fidelity should be able to reach, and in some cases, even surpass that of the PS4, with a potentially massive boost in fidelity and/or frame rate when docked.
For Ray Tracing, there will only be 12 RT cores, so don't expect too much beyond ray-traced shadows and maybe some lightly ray-traced lighting.
One current big unknown is the frequency of both, the CPU and GPU. It's hard to find specific performance metrics for the Cortex A78C, but it comes in 6-Core and 8-Core configurations, with varying frequencies. I was able to find information on a 6-Core version used in Qualcomm's Snapdragon XR2 Gen 2. Bear in mind, however, that this could also be a custom version of the chip, and below is only to showcase some possibilities. The Switch 2 will use an 8-Core configuration, but I have yet to find any information on an SOC that uses an 8-Core model. As for GPU frequency, there is virtually no data that we can currently extrapolate on.
6-Core Cortex-A78C specs on the Qualcomm Snapdragon XR2 Gen 2

Let me know if I'm missing anything, or if any of this information is incorrect.