I see you are not short of suggestions! Here is an article I wrote for determining the sex of hoverflies. It was originally intended for the UK but the principles can be extended beyond; and if you stick to the subfamily Syrphinae there are no exceptions to the general rule outside of a couple in New Zealand!
We’ve done the UK pretty well now, and through the Syrphing Europe project we’ve made some progress on the rest of the continent, but that’s a lot more to do!