I have an older prohormone article on Mesomorphosis
which has value in some general areas of description. Some areas where later-acquired knowledge contradicts the article are: norandrodiol (nor-4-AD) does not normally cause erectile dysfunction (the article speculated it might); effective transdermals are available (they were not at the time of the article); inhibition of LH production is less of an issue with 4-AD than I then thought and expected; and 4-AD shows inherent activity rather than relying on conversion.
Another article there is the one on enzymatic
The T-mag site has an article on MAG-10 that also discussed prohormones in a more current light.
Besides all this, a fast summary is, 4-diols have inherent activity whereas diones do not
and the 1-diol has little or none; 17-ol-3-one
compounds (e.g. androst-1-ene) are directly active; diols have no direct conversion to estrogen whereas diones do; 1-compounds don’t have even indirect conversion to estrogen or are even indirectly substrates for 5alpha-reductase; and 5-compounds are estrogenic. That doesn’t say everything but does cover a fair bit. Other than that I would read various articles and search the Forum. Hope this helps!