It will gradually become cool in Nov. The temperature differs much in day and night. It is usually 22-28 degrees during the day and 15-20 degrees at night. Long sleeves and jackets are OK.

The days you want to spend in Guilin depends on what do you want to see there. Generally speaking, three days are enough for you to visit it.

You find some useful information on how to plan your trip here:
https://www.travelchinaguide.com/package/guilin.htm
Hope it can help you to make your route.