By default, every sample project in Single connection SDK for tlsr8258 has build setting with Optimization level -O2 ( if opened in Telink IDE). Is this a strict restriction for all cases? Should the FW and SoC HW work fine, if we change for other variants (O1 or Os)?

I've already tried to switch one of my long-developed projects to -Os (to get smaller fw image), which utilize BLE radio, SPI, I2C, UART, Timer and some other peripherals, including handling the dedicated IRQs. And after that change, looks like the FW app doesn't really start well. So i wonder if there some rules to follow when changing build Optimization level, unspecified by Telink?