I also agree with Sheila's comments.
My current carbon road bike is a WSD Madone, which I bought before Trek introduced Domanes and Silques and Emondas (and I honestly don't understand the differences between them). It was a mid-range carbon road bike at the time. Almost immediately I noticed a difference between it and my old aluminum Trek road bike -- it definitely has a smoother ride on bumpy pavement.
The wheels and tires do contribute to the smoothness, though -- a few years later I bought new Bontrager wheels and noticed a much harsher ride. I have since switched to relatively low-cost Mavic wheels which are much better.
I have not really noticed any other difference between carbon and aluminum. I am an average-speed rider who prefers to ride a comfortable pace and enjoy the scenery while faster, more competitive people race ahead up the road. If I tried to go fast, maybe I'd notice more differences.
The WSD geometry, however, did make a huge difference to me. The old aluminum bike was a men's frame, and the reach was too long for me. Having a smaller more compact handlebar has also made a huge difference in comfort and allows me to ride in drops and reach the brakes easily. The only changes I made to the setup of the WSD Madone was to switch to a slightly narrower version of the handlebar that came on the bike, and to get a different saddle.
One thing I notice is that the Liv you're considering has an 11-32 cassette, vs 11-28 for the Emonda and the Merida, which means it has 1 or 2 cogs that are easier for riding up hills. If you ride in a hilly area, that could make a difference. Of course it's also possible to replace the 11-28 cassette on the Emonda, Merida or other bike with an 11-32 (or one with different sized cogs) if you find the 11-28 is not ideal for you. But it's worth noting when you test bikes -- if one seems easier on hills than another, it could be due to the gearing rather than the frame material or geometry.
Good luck!
- Gray 2010 carbon WSD road bike, Rivet Independence saddle
- Red hardtail 26" aluminum mountain bike, Bontrager Evoke WSD saddle
- Royal blue 2018 aluminum gravel bike, Rivet Pearl saddle
Gone but not forgotten:
- Silver 2003 aluminum road bike
- Two awesome worn out Juliana saddles