Yes, these watches are new. However, you should know that such a watch only runs for about 52 hours at a time and then you have to charge it again. The SE also doesn't have an Always On Display. So most of the time you wear an Apple watch that doesn't show the time, unless you raise your arm.

There are various other models from other manufacturers that have an Always On Display and still run for about 7 to 20 days without recharging. It's not from Apple, but if it's only about fitness, maybe that would be an alternative? The latest Amazfit GTS 4, for example, runs for about 8 to 16 days, has a 3GB music memory (2.3 GB usable):and Bluetooth phone call functions. It can also do fitness with 150 different sports :-).

Amazfit GTS 4 (43 mm, aluminium, plastic)

Yes, normally

Thanks for the answer and the suggestion, I'll have a look at the Amazfit.