No thoughts on thickness as ours is 3cm, but we have Barroca and I would never do that again. It is a very, very soft stone--on ours, we have pitting all over the surface after only two years and you cannot, for instance, set anything with a ridged bottom (olive oil, beer, wine, etc.) down without a coaster or you will get a permanent imprint. The softness may vary somewhat based on the quarry and distributor (ours is two years old and purchased on the West Coast) but test it extensively before committing to it. I really wish we had paid more for a harder stone. (I did find that soapstone was cheaper than most darker granites where we are when we were looking, though, which was a surprise!)

I went with a straight edge, as I wanted a sleek look, but I did not know that such an edge would make a laminated seam more visible (I learned that later!) Even so, I'm glad I went with a straight edge. I "saw" the seam for about a week, and now I dont even notice it. Here's what it generally looks like: Here's the seam with direct sunlight light making it look as bad as possible:

4cm is a good look. It will look good if done by a competent fabricator, one whom you should choose carefully. You get what you pay for. You can always ask them to produce a small mock up.

I only wanted Verde Fuoco, and the 3cm slabs were too pink. We have an eased laminated edge. There really isn't a reason for concern: If you want no laminated edge you can have it; if you want a thicker look you can have it. Lily's kitchen is brilliant and she hated the look initially, but realizes that there is no reason to sweat it. BTW I'm a west coaster and found plenty of 3 and 2 cm slabs. Maybe on the east coast there isn't any 2cm rock, but I didn't find it typical at all that there was only 2cm. In fact I found a lot of 3 cm rock (Portland and Seattle). My rock is a little hard to find, so the slab I wanted happened to be in 2cm. no problem (but you need a plywood underlayment).