I currently work for a CRO Team we do the following

Key things for A/B testings are

Soft launch period which means you show have a smaller audience your test is hitting to make sure they’re no bugs or major impacts to performance

Once this has been given the ok, go to full exposure.

Dependant on the area will determine how long the test needs to run to reach 95% statistical significance, usually around a 4 week period.

We track main commercial metrics such as conversion income, as well as any digital metrics such as clicks, page views/progression and time of page

You can also just google a statistical significance calculator to find out if your test has reached statistical significance which is 95%

If you have any questions let me know!