Using iGO Primo (2.4) 9.6.29.468978 with the TomTom 2014Q2 maps on Android.

How does one control the amount of 3D buildings displayed at any given time and the distance they get displayed/faded out?

3D buildings work with my current setup but they are only displayed at very close proximity of your location and then only one or two at a time.. kinda beats the purpose of having 3D buildings enabled as they don't really add anything to it this way imho.

I researched possible sys.txt entries that (should) control this but it doesn't seem to make any difference on my device.

This is one of the reasons that I like my iGO8 much better because I can control those things for the most part.

EDIT: I see you say Android. Sorry, but iGO8 is not available for Android.

No, you don't have iGO8 on Android.