Update, August 20, 2025 (7:35 AM ET): Just a few hours after this was first published, AYN released more specs for the upcoming Thor handheld. It will indeed be very similar in size to the New Nintendo 3DS XL, measuring 150 x 94 x 25.6mm (vs 160 x 93.5 x 21.5mm for the 3DS XL). It will weigh slightly more, coming in at 380g vs 330g.
Interestingly, there are two options for the processor: Qualcomm Snapdragon 865 or Snapdragon 8 Gen 2. The former is the same as the Retroid Pocket Flip 2 and Pocket 5, and the latter is the same as the Odin 2. Both should play the entire 3DS catalog to some extent, although the Snapdragon 865 may struggle with two screens and upscaling. Further testing is required here.