I thought I'd do a quick round-up of what we know, and give some general idea of how big our margin of error is on the known and unknown variables on the new chip.
Chip
Codenamed Drake/T239. Related to Orin/T234. We don't have confirmation on manufacturing process. The base assumption is 8nm (same as Orin), however kopite7kimi, who previously leaked info about the chip and said 8nm, is now unsure on the manufacturing process. The fact that the GPU is much larger than expected may also indicate a different manufacturing process, but we don't have any hard evidence. We also don't know the power consumption limits Nintendo have chosen for the chip in either handheld or docked mode, which will impact clock expectations.
GPU
This is what the leaks have been about so far, so we have much more detailed info here. In particular, on the die we have:
12 SMs
Ampere architecture with 128 "cores" per SM, and tensor performance comparable to desktop Ampere per SM. Some lower-level changes compared to desktop Ampere, but difficult to gauge the impact of those.
12 RT cores
No specific info on these, in theory they could have changes compared to desktop Ampere, but personally I'm not going to assume any changes until we have evidence.
4MB L2 cache
This is higher than would be expected for a GPU of this size (most comparable would be RTX 3050 laptop, with 2MB L2). Same as PS5 GPU L2 and only a bit smaller than XBSX GPU L2 of 5MB. This should help reduce memory bandwidth requirements, but it's impossible to say exactly by how much. Note this isn't really an "infinity cache", which range from 16MB to 128MB on AMD's 6000-series GPUs, it's just a larger than normal cache.
Things we don't know: how many SMs are actually enabled in either docked or handheld mode, clocks, ROPs.
Performance range in docked mode: It's possible that we could have a couple of SMs binned for yields, as this is a bigger GPU than expected. This would probably come in the form of disabling one TPC (two SMs) brining it down to 10. Clocks depend heavily on the manufacturing process and whether Nintendo have significantly increased their docked power consumption over previous models. I'd expect clocks between 800MHz-1GHz are probably most likely, but on the high end of expectations (better manufacturing process and higher docked power consumption) it could push as high as 1.2GHz. I doubt it will be clocked lower than the 768MHz docked clock of the original Switch, but that's not strictly impossible.
Low-end: 10 SMs @ 768MHz - 1.97 Tflops FP32
High-end: 12 SMs @ 1.2GHz - 3.68 Tflops FP32
Obviously there's a very big range here, as we don't know power consumption or manufacturing process. It's also important to note that you can't simply compare Tflops figures between different architectures.
Performance range in handheld mode: This gets even trickier, as Drake is reportedly the only Ampere GPU which supports a particular clock-gating mode, which could potentially be used to disable SMs in handheld mode. This makes sense, though, as peak performance per watt will probably be somewhere in the 400-600MHz range, so it's more efficient to, say, have 6 SMs running at 500MHz than all 12 running at 250MHz. Handheld power consumption limits are also going to be very tight, so performance will be very much limited by manufacturing process. I'd expect handheld clocks to range from 400MHz to 600MHz, but this is very dependent on manufacturing process and the number of enabled SMs.
One other comment to make here is that we shouldn't necessarily expect the <=2x performance difference between docked and handheld that we saw on the original Switch. That was for a system designed around 720p output in portable mode and 1080p output docked, however here we're looking at a 4K docked output, and either 720p or 1080p portable, so there's a much bigger differential in resolution, and therefore a bigger differential in performance required. It's possible that we could get as much as a 4x differential between portable and docked GPU performance.
Low-end: 6 SMs @ 400 MHz - 614 Gflops FP32
High-end: 8 SMs @ 600 MHz - 1.2 Tflops FP32
There is of course DLSS on top of this, but it's not magic, and shouldn't be taken as a simple multiplier of performance. Many other aspects like memory bandwidth can still be a bottleneck.
CPU
The assumption here is that they'll use A78 cores. That isn't strictly confirmed, but given Orin uses A78 cores, it would be a surprise if Drake used anything else. We don't know either core count or clocks, and again they will depend on the manufacturing process. The number of active cores and clocks will almost certainly remain the same between handheld and docked mode, so the power consumption in handheld mode will be the limiting factor.
For core count, 4 is the minimum for compatibility, and 8 is probably the realistic maximum. The clocks could probably range from 1GHz to 2GHz, and this will depend both on the manufacturing process and number of cores (fewer cores means they can run at higher clocks).
The performance should be a significant improvement above Switch in any case. In the lower end of the spectrum, it should be roughly in line with XBO/PS4 CPU performance, and at the high-end it would sit somewhere between PS4 and PS5 CPU performance.
RAM
Again, the assumption is that they'll use LPDDR5, based on Orin using it, and there not being any realistic alternatives (aside from maybe LPDDR5X depending on timing). The main question mark here is the bus width, which will determine the bandwidth. The lowest possible bus width is 64-bit, which would give us 51.2GB/s of bandwidth, and the highest possible would be 256-bit, which would provide 204.8GB/s bandwidth. Bandwidth in handheld mode would likely be a lot lower to reduce power consumption.
Quantity of RAM is also unknown. On the low end they could conceivably go with just 6GB, but realistically 8GB is more likely. On the high end, in theory they could fit much more than that, but cost is the limiting factor.
Storage
There are no hard facts here, only speculation. Most people expect 128GB of built-in storage, but in theory it could be more or less than that.
In terms of speeds, the worst case scenario is that Nintendo retain the UHS-I SD card slot, and all games have to support ~100MB/s as a baseline. The best case scenario is that they use embedded UFS for built-in storage, and support either UFS cards or SD Express cards, which means games could be built around a 800-900MB/s baseline. The potential for game card read speeds is unknown, and it's possible that some games may require mandatory installs to benefit from higher storage speeds.