I can can read in BGM13P Data Sheet than i can supply the module with inside this range 1.8 to 3.8 V.
I am using some sensors which need power supply of 1.8 Volt. I am thinking about power supply all my system with 1.8 v. Is it a good idea ?
my understanding is that you could use. but you may need to consider a very stable power source ( ripple under different load and load change).
you may consider some factor like RF output power, BOD need work reliably with your power supply.
you may loose this a bit, for example you may have 2.1V power for BGM, but connect your 1.8V sensor (like I2C, SPI, UART) directly with BGM. the 1.8V level may still within the BGM GPIO spec. refer to the datasheet to see the data like VIL/VIH.