My general concern reading this thread and your earlier thread might be summarized as the grass is not always greener on the other side of the fence. It is very possible to transfer and then discover that you are not at a place that is any better than where you already were, and that might even be a worse fit. Also, there are some potential downsides to transferring.
As an example, there are significant advantages to getting to know your professors. These advantages include things like improving access to internships or research opportunities, and sometimes just professors suggesting classes that you might want to take or books that you might want to read. One big advantage at a smaller school such as Carleton is that it is usually easier to get to know your professors. However, transferring means that you leave the professors and the friends that you were starting to know and need to start all over again.
There is a tradeoff between “chill” and “intellectually rigorous”. Highly ranked schools which are intellectually rigorous often are quite academically demanding, which takes away from the “chill” aspect. I am for example thinking of Stanford as having some sense of “California chill”, but I also remember piles of homework and very frequently (probably most of the time) doing homework on Saturday afternoons there, which sort of limits the extent to which it could really be called “chill”.
Also, Carleton College is a very good college. To me it is already very high on the “intellectually rigorous” and yet also somewhat “chill” list. If I am remembering correctly there are multiple Pulitzer Prize winners who graduated from Carleton, and you can do very well with a degree from there.
And moving to a new college or university is always a very significant disruption in a student’s life. It does take some time to get used to this change.
Looking at suggestions above, to me Cornell does not seem “chill”, although the location is beautiful. “Academically demanding” is perhaps how I would describe Cornell. UVM does seem to have some combination of academically strong and chill. It is larger than Carleton which would imply a wider range of potential majors. UVM is a bit expensive unless you qualify for a very good merit aid, and I do not know whether this is available to transfer students. To me Williams seems unlikely for acceptance as a transfer student, and not particularly chill. U.Wisconsin reminds me a bit of UVM, but is a bit higher ranked for my major (mathematics) which probably should not matter at all to you.
All of which makes me wonder whether perhaps you might want to stay where you already are and take some more time to find your way there. Carleton really is a very good college. I have read that they have a beer Olympics which I might personally try to avoid, but otherwise it seems like a good place to be for four years. I am confident that employers and graduate schools throughout the USA know how strong Carleton is.
And no college or university is perfect. You will find some annoying people and probably a few bad professors just about anywhere. You will also find quite a few academically strong students and many good professors at any college or university mentioned in this thread, and also at a few hundred other colleges and universities throughout the USA and abroad.