ESP32 have 3.3V, what resistance for DS18B20?

The Arduino has 5V, so even on a 15 meter CAT5 cable, the DS18B20 with 4K7 worked for me. But what about ESP32 and 3.3V? Here 4K7 is probably stupid because it is a reduced voltage of 3.3V. Which optimal resistor to choose?

It all depends...you might try 4k7 as it could still work. If it doesn't, try 3k3 as it gives roughly the same current/pullup strength at 3.3V as 4k7 does at 5V. If that still doesn't work, you need to rethink your cabling layout as OneWire should easily work over a distance of 15 meters with simple pullups. At such distances, active pullups / line drivers aren't really necessary.