Using my multimeter, measured 436mA drawn before the LDOs, for the OSD circuit. Does not include MCU current.
Measured 260mA drawn after the LDOs on the 3.3V supply. Measured 70mA on the 1.8V supply. (All using the Amps scale, on the 10A unfused input).
If this is accurate, then I might be able to achieve around 360mA using a switching power supply with 80% efficiency (not including MCU current draw).
Weka OSD 