As Moomomie said, the vast vast majority of illegal dug addicts also drink (though aren't necesarily alcoholics)
In terms of danger to the baby, alcohol is the most dangerous - definitely more likely to cause long term issues than heroin, cocaine, meth etc etc.
It wouldn't necessarily be clear at all that a child has been affected by drugs - if a child has FAS (ie. the facial features) then it's obvious that alcohol has caused this problem. Also as Moomoomie said, drugs which cause physical dependency (eg. heroin) will cause physical dependency in the fetus as well, so after birth the baby has to go through withdrawal which can just be awful to see and requires specialist medical care. That will also be obvious at the time
Otherwise, you're talking only seeing issues years down the line, frequently sensory issues, ADHD, behaviour issues, learning issues and so on. The problem is that you can't easily pick apart, and may not at all be able to tell which drug caused an issue, or whether you're dealing with something which the child would have had anyway even if they weren't drug exposed
Apart from physical withdrawal, physical problems in pregnancy and soon after birth (prematurity etc) and all the alchohol related disorders, we don't really have any conclusive evidence that a certain drug causes certain issues later in childhood. Some drugs are linked to behaviour issues, sensory issues etc, but it's not definitive, and anecdotally you'd find massive variation - children who have been exposed and seem to have major difficulties and children who've been exposed to many drugs and are doing brilliantly with few or no apparent issues. Basically the only conclusive stuff is around things like miscarriage risk, low birth weight risk etc, not learning or behaviour issues, except with alcohol
I can't really help with a website because I've never seen a very good one which has helpful explanations for each drug, especially related to issues later in childhood.
Personally I would be most worried about alcohol exposure because there's definitive proof it can have very serious effects, which will be permanent