Understood like this-----
optimized qvd-- data fetch from data source and store into qvd without any where clause,conditions is called optimized qvd.in optimized qvd only you use exits function in where clause.
non optimized qvd- data fetch from data source with conditions and calculations then store in to qvd is known as non-optimized qvd.
Qvd optimization is not about fetching data from database and storing to qvd .
Its about loading data from qvd to RAM.
So when we are loading our application from qvd without any transformation , without any where clause load is optimized
if we do any transformation load is not optimized except exists() function.
You should check out the post from a while ago from stevedark
It's one of the nicer explanations i have seen of optimised loads.