Would most people have heard of the Ancients. Yes.
The ancients are widely known of, though the vast majority of people will never have seen an Ancient artefact or ruin. They would be much like the ancient Egyptians are to us. Just about everyone will have heard of them, many may have seen TriDs of ruins. Subsector news agencies would run stories of some explorer finding a ruin or relic. Few people would have any detailed knowledge but most people would have heard of them.
Lets face it many people will have seen them in B movies and the like, "Wrath of the Ancients" Our hero Chuck (the beard) Norris exploring the strange ruins on world B23847 uncovers an ancient evil that threatens the Universe and only he can defeat it (and save the romantic interest).
Would most people have heard of Grandfather. No.
Grandfather, the Ancient wars etc are a detailed subset of Ancient Knowledge known only to an interested few. Only specialists in the Field are likely to have any real knowledge. People may have heard stories in much the same way that people may be familiar with Tutan Kharmun but only due to the stories that did the rounds with the curse.
Would most people have heard that the Vargr are uplifted Earth dogs. Yes.
This is the sort of thing, like humans having evolved from monkeys, that most people will have heard. Some will say they don’t believe it (the Vilani for one since it supports Solomani claims to being the “True” Humans), others will repeat it often to mock or belittle the Vargr (a lot of people along the borders with them or who suffer raids).
Would most people believe in links between the Droyne and the Ancients. No.
Again this is the sort of detail that specialists would be aware of but the bulk of the population who may have heard it ignore it or dismiss it out of hand. After all the Ancients build planets and did incredible things. The Droyne are just another alien species in a verse with many aliens. In much the same way the speculation about chirpers and Droyne is also all but unknown or disbelieved. For the general population to accept that the Droyne are linked to the Ancients is to accept the fact that they are vastly older than Humaniti and that they are (or were) vastly more advanced. That whole idea brings an awful lot of baggage with it and would be denied or disbelieved for many reasons.
Consider today, the Egyptians had a vast and advanced empire (for the time anyway) while we in the west were wearing animal furs and using sharp sticks with bits of flint tied to them. The Chinese had an empire larger than all of Europe and which had technology far in advance of anyone else of the time. Europeans do NOT regard either country as superior today and in fact both are considered technologically backwards compared to the western world. Asking someone off the street if they consider China to be a more advanced country because they had medicine and gunpowder long before us and the answer is going to be no.
I see it being the same with the Droyne. Myths and Legends about them being a super race thousands of years ago are just that, bar talk and jump tales. In the 3rdI they hold some planets and are about as advanced as the Imperium is. No super race there.
There is a wide gap between people having heard of something and people believing it. Many will have heard of the Droyne being something to do with the ancients. Many have also heard of the Candy Man, Freddy Kruger, Father Christmas etc.
