There has been a lot of talk that the R7II will not have a mechanical shutter... only an electronic shutter. In order to accomplish that, Canon MUST vastly improve sensor readout speed to minimize rolling shutter issues. A stacked sensor is one way to do that.
So it makes sense that the R7II would have a stacked sensor. Especially since it would also improve auto focus performance, which is another area where the original R7 comes up a bit short.
The form factor change SHOULD BE nothing more than adopting the proven control layout of other Canon cameras like the R5II etc.
No, I don't believe Canon will give the R7II an R1 or R3 style body, with built-in battery grip. At least, I certainly hope not! But they do need to make the R7II compatible with a battery grip. Ideally would be it sharing the same grip(s) used by the full frame models. That is probably why the body will be slightly larger... although the original R7's footprint was very close to that of the R5's. There was just a few millimeters difference, which is why it was so sad the original R7 couldn't be fitted with a BG-R10.
Likely a truly improved R7II will cost more than the original... perhaps in the $1800 to $2100 US range. But keep in mind that the original 7D sold initially for $1700 and the 7DII for $1800... in 2009 and 2014 respectively! Both of those sold like hot cakes! It's baffling why Canon felt the need to cheapen the R7 and give it an introductory price of $1500 in 2022. Between 2014 and 2022 inflation was almost 24%... so theoretically the market shiould have welcomed a modernized, mirrorless 7DII that cost over $2000. Instead Canon went the other direction.
While there was a lot to like about the original R7... however there also were a lot of disappointments. Let's hope Canon has been paying attention customer comments about the R7 and R7II!