I got my KW88 some weeks ago and wrote a review (in german). Btw: the german translation in the menu is horrible (offered help, but got no response).
The KW88 is using a MT6580M with 1 GHz and 512MB RAM. Data connecting will be stopped, the moment it turns off. As in all other watches. So, no push notifications if you are using a nano-sim. The companion apps is still in development and not much of use.
Build quality is “nice” although i don’t like the plastic on the back and on the front. The straps is far too long and not very well build. Btw. GPS is only working if you activate GSM / WLAN too. GPS alone is NOT working.
At the moment there are NO customs watchfaces and i wonder if they will iron out and update the firmware bugs the next coming months.
Is it worth the 100 Euro? Probably, if you are “in watches”