For example, you have this in your config right now:
[aero]
PrimaryBalance=0.08         ; Controls normal layer opacity. If you turn this up to 1 the window will be fully opaque, for example. Ranges from 0 to 1

Active_SecondaryBalance=0.43    ; Controls the multiply layer intensity for active windows. Ranges from 0 to 1.
Inactive_SecondaryBalance=0.43    ; Controls the multiply layer intensity for inactive windows. Ranges from 0 to 1.

Active_BlurBalance=-0.125    ; Controls "overexposure" effect for active windows. Ranges from -1 to 1
Inactive_BlurBalance=0.365    ; Controls "overexposure" effect for inactive windows. Ranges from -1 to 1 

For 2.1.0, this is how these settings would translate:

[config.aero]
activeColorBalance=0.080000  
inactiveColorBalance=0.032000 ; altalex for some reason didn't do * 0.4f so its always 40% of the active color, so you have to do the manual work
activeBlurBalance=-0.125000   ; these settings translate perfectly, just copy the values from your old config.ini
inactiveBlurBalance=0.365000

you may notice there is no secondarybalance here, just set the OPACITY OF YOUR TITLEBAR BLEND COLOR TO THE SECONDARY BALANCE YOU WANT. for example, here the config says 0.43 secondary balance for both active and inactive, so you would set your titlebar blend color opacity for active/inactive to 43%. This isn't a fixed value, make sure to match up with whatever color you want. If you have overrideaccent = true, for SIB you can just match up the color and opacity of the DWMBlurGlass colors.