I've been a huge fan for over a decade of the "sport watch" genre and have followed (and owned) many of the Garmin Fenix watches this is designed to go head to head with... some comments.
1) I suspect what we are seeing is the new flush button on the left side of the case will by default (I bet you can configure it differently) be what is today the flush button on the right of the Series 7. It will be the button that takes you to the app list, or however you have configured it.
2) The crown will be similar in use to today's crown, however those using WatchOS beta 9 know that now the crown cycles between pages of information in the fitness app and holding it down is what starts and stops water mode.
3) The button on the right below the crown will be devoted to fitness functionality, specifically acting as a lap button, start/stop button etc. This is SO useful as the touchscreen during sports is very difficult or impossible to use (sweat, etc. all make it difficult) so currently we have to use "kludges" of pressing the crown and the flush button at the same time etc. which itself is tricky to do. This will make it a much more proper sports watch.
The questions that are begging to be answered...
1) There has to be something more to the software. The improvements in WatchOS beta 9 are excellent for running, but the watches this targets are "kitchen sink" sports watches that in very sophicated ways track biking, swimming and more. For example you'd expect this to be able to sync to cadence and power meters (that measure force from your foot) on bikes. You'd also expect built in topographical terrain maps and hopefully the ability to make courses in advance and load them into the watch for hiking.
2) On further notes for the software, all the competitors are now attempting to combine your fitness life into holistic measurements of "readiness" or a score that tells you how over or under-trained you are. There are hints this is being developed in WatchOS beta 9 but not yet specifically shown. Maybe this watch? Without it would be a big miss.
3) Battery life. The competitors have between 5 day and 21 day battery life, and all do at least 18 hours of GPS recording non-stop, most over 24 hours. I think Apple has to target a minimum of 3 days of normal battery life and at least 24 hours of GPS sports recording to be competitive. I don't think they need the week+ of the competitors which at this point is more for bragging rights than need (aside from the most ambitious ultra duration athletes or through hikers) but you have to be able to set out on an Ironman triathlon, or entire day hike and not run out of battery.
4) The most common size for these "super sports watches" is 47mm, so bigger than the Apple Watch Series 7 at 45 mm. Garmin offers a larger speciality size at 51mm but that is pretty niche, and not their best seller at all. The rumors here indicate the case is 49mm, I assume vertically since that has always been the largest dimension on an Apple Watch. Frankly, that's huge. I have small 6.25" wrists and this watch is likely going to look foolish on me. You never win style points with a big sports watch but I'm surprised the rumors indicate Apple went this large, to me it is going to look strange in the extreme on most women, and a good percentage of men. 47mm has always been the standard for good reason, it still looked kinda dumb but a decent percentage could pull it off. It also is going to introduce a new 3rd size of band based on rumors so you'll have to purchase new straps to make it look nice, although just like with the 41mm straps that fit the 45mm (but don't sit flush with the case) you'll in theory be able to use your old 45mm straps, they will just look improper. I really, really hope there is a surprise and a 45-47mm sized version of this, or that the 49mm rumor is wrong.
The two most famous reviewers of sport watch tech, each for a decade plus, are DCRainmaker and DesFit. For the first time ever they have been invited and are attending the Apple Watch announcement in person so that says something about who Apple is targeting.
https://www.dcrainmaker.com
https://www.youtube.com/c/DesFit