The "Venu" line of watches from Garmin are their "lifestyle" watches. They are more toned down from the more tactical look and feel of other Garmin watches.
The Venu Sq 2 was just recently released. I have the Venu 2, myself.
Missing from your list:
* <10mm thickness - it appears to be a smidge over
* hackable - You have a Fenix 7 so you're familiar with the ecosystem
* always-on screen - it's OLED and not always on, but works well enough - there is an always on mode but it's not recommended for OLED
As for the rest:
* >7 days battery life - Venu 2 is rated up to 12 days, I charge about once a week
* HR monitor - it's there, works reasonably well
* toned down - as a lifestyle type, it's a bit more toned down
* high-contrast - it's as high contrast as any OLED, and clearly visible in sunlight
* buttons - 2 of them
I'd throw in cost as a valid metric. The Pebble watches were really inexpensive and I think that's what brought more broad appeal to them early on. My Venu 2 was $400. That's a tough pill for some to swallow.