They all look good so far. Here are my current thoughts
Artists: The +1 health on top of the culture looks strong and I can see +2 being a seizable portion of your total culture per turn boosting your virtue acquisition a lot. I would definitely recommend artist if you want to go prosperity since this seems to be the tree with the most bonuses to grab early to be interesting (free settler, free worker, +2 pop per new cities etc).
Engineers: From what we've seen, hammers seem to be a more scarce ressource in civbe than in civ5, hills being only 1 hammer base for example. Also the trees seems to have less free hammers than early civ5. You can still grab free settler and free worker but that's it compared to civ5's +1 hammer, free monuments, free aqueducts, free worker, free settler. And that's only if you go prosperity early in which case artist seems like a better option. Getting +2 hammer makes your capital on flat go from 4hammer to 6 and outpost on grass go from 1 to 3 (before tiles). That is a tremendous difference if we have to bring up a lot of infrastructure. It will also be very good, as liberty republic was, for people wanting early military. Since you make the gambit to raise your food through terrain then, these colonists should in my opinion take the free worker to catch up in food and just build a soldier if necessary (which production is hastened up to 50% thanks to engineers). Or maybe take the lab to have the free tech in order to have more options for production if it appears teching is too slow and you'd finish all your early choices.
Refugees: Very good if food is as important in this game. It's somewhat the other side of engineers, allowing you to raise your food rather than your hammers so you'll have to rely on hills for hammers, sadly base hills seems to be only 1 hammer in this game.
Scientists: Will depend on how important it is to tech fast in this game compared to being able to have a strong infrastructure. Also it will depend on whether or not +2 per city is strong compared to your base bpt. It will definetely boost your early bpt so maybe scientists are a definite very good option if there are early techs that you want fast for some reason.
Aristocrats: +1 health is good like for artists. We'll have to see what kind of ratio the game use for gold per hammer to really see how good this is.