I have both in use. The new Nest Mini sounds much better than the Google Home Mini. It is minimally thicker, and also has a "hole" on the back so that it can be hung up easily.
The Google Nest Mini has a range that mainly depends on the Wi-Fi coverage in your home. The Nest Mini supports Wi-Fi 802.11b/g/n/ac (2.4 GHz/5 GHz), which provides good range and stability.
For voice control with Google Assistant, the effective range is about 5-10 metres, depending on the volume of your voice and any obstacles such as walls.
Should be version 2. According to the article number, the only difference is EU/US. This seems to me to be the target market. In other words USA and EU. I would therefore go for the EU. But I don't know exactly.
Of course, there are actually two variants, one of which was actually the old one, which is no longer available. This Google Nest Mini can do everything, including Multiroom.
For even better sound, however, I would use the Google Nest Audio, which can also do everything the small ones can do, but they definitely sound even better.
Google Nest Audio (Google Assistant)
These are the same products, there are no differences in the functionality of the Google Nest Mini, but the Google Nest Mini 2 are better, because they have better speakers. They all have Wi-Fi too :). Be careful when placing on coated furniture, the rubber underside of the Google Nest Mini can stick so much to coated surfaces that it can happen that a bad coating tears when lifting the Google Nest Mini (happened to me, these rubber surfaces at the bottom seem to really stick to coated surfaces, which of course they don't but better put something under there).
Yes, you can combine several of these devices into a speaker group in the Google Home application. You can also set up a stereo pair.
Another interesting solution for better sound might be Google Nest Audio, which is a bit more expensive but sounds much better.
Google Nest Audio (Google Assistant)
No, these are Google Speakers that work with Google Home and Google apps. They are not bad, but there is the better Google Nest Audio, which sounds even better.