What I feel is, this is the concept of high risk high return. In the stage of pre-ICO or private sale, you take higher risk than ICO, if theproject turn out to be a successor, you will get a high return. Same way, the possibility for the project to fail or become a scam is also high.
I do not see any connection at what stage to invest and how it is connected will the project become a scam or not.
Obviously, before selling it is better to do it.
If the ICO is good, then it will easily collect at least software.