Smaller size in the same model of bike is going to put your bars lower if your saddle is at the proper height on them. Saddle height is the all-important measurement on a road bike that will pretty much be the same for all road bikes you try on no matter the size of the frame.

So I'm having a little trouble understanding why you say you want a more relaxed position but then say that a smaller bike, which shouldn't have given you a more relaxed position, actually felt better. Did you just set the saddle height to be even with the bars or some other such?

Typically it's expected bikes with a higher stack to give you the more relaxed position. But you do also have to consider their effective top tube length or reach from the saddle to bars/hoods. Which will vary somewhat from one model to another and from brand to brand. Though they are similar as most brands build to their average customer dimensions. So if you are an outlier in that, then you might need a custom bike or learn to adjust and change what you need to adjust and change.