A watch dog timer (WDT) and two multi-counter WDTs (MCWDT) are available for timing and interrupt generation in deep sleep mode.
WDT = 16-bit, MCWDT = 3 counters (16-bit, 16-bit, 32-bit : cascadable to 64-bit)
Note that in deep sleep, all high speed clocks are off and Timer peripherals (TCPWM) are not active.
I am not familiar with the MCWDT, but I read the brief document about it.
Can the period be adjusted after it's started? This is necessary if the timer is to be used in tickless mode as the RTOS tick source.
Yes, the period can be adjusted dynamically. Or locked out to prevent accidental changes.