Finally done Angel Eye Brightness coding. Yes it does work for my DTEC CREE AEs (I heard LUX AEs has built in capacitor to negate the coding effect, so I feel lucky to have purchased these DTEC ones).
First of all, coding needed to turn on Angel Eyes (my LCI E90 has a FRM3_E89.C32 NFRM module):
TAGFAHRLICHT_ECE_1 --> aktiv
VERHALTEN_DRL_TFL --> drl_s
DRL_TFL_MIT_SL_1 --> aktiv
Now with NETTODAT coding (I used NCSDummy), coding the following will alter the angel eye's voltage to 12.5V at all times (again in FRM3_E89.C32)
PWM_SL_1_FKT_BL_TFL --> 0B, 1C
PWM_SL_1_FKT_PARKL --> 0B, 1C
PWM_SL_1_FKT_SL_TFL --> 0B, 1C
To alter the voltage (i.e. the '0B, 1C' part), use this formula:
Voltage * 4095 digits / 18V = the value to code (hexadecimal)
Now I have bright(er) AEs day and night.