Q: Page 60 & 61. In general, are there straightforward criteria to know if the board has a high conductivity or low conductivity?

If the conductivity is known, there is no problem since a limit value of 15W/m.K has been defined. Otherwise, "low conductivity" generally applies on boards which have surface metallization only (typically for microwave functions). A board which has more than two internal layers (power supply + ground), should be considered as a “high conductivity” board.