Howdy
Wasn't very satisfied with the recent comparisons I'd seen on YouTube and on the internet in general so I made my own!
I have compared a man-at-arms from the starter set to a bloodreaver, blood warrior, Neave Blacktalon, a blood secretor, an exalted deathbringer, and the darkoath warqueen.
Conquest size comparison
https://imgur.com/a/9MCeTLR
Last but not least and what surprised me the most was the imperial mages. They actually scale pretty well with these guys. Obviously none of its perfect but I actually enjoy how close they are all together. Makes a stormcast eternal look more like just another foot knight, which I'm good with.
Obviously not everything's going to work together, for me I'm thinking specifically of using these for dungeons & dragons. But my main investments in Warhammer is Khorne bloodbound and stormcast eternals, which as you can see mesh pretty well.
One thing I do want to mention, I don't have any khorne skull crushers on hand yet but I imagine they would work pretty well in comparison to the calvary from conquest. The horses are huge, so normal Calvary, even from chaos knights, will not do it.