Hi chaoticelf13,
Bottoming out is actually a function of the entire mattress not one particular layer and only happens when the entire mattress has compressed to its maximum which won’t happen with any of their mattresses. The comfort layers of these mattresses are 4.5" (the quilting foam and the latex) and the latex can be chosen for firmness level so the goal is to “go through” softer comfort layers just enough so that the transition into the firmer support layers is “just right” without the firmness of the lower layers coming through too much for some body types or the comfort layers themselves being too firm for comfort/pressure relief for others. They are very good at helping you choose.
The Ultra Plush and the Eurotop use the same materials (your choice of firmness level of blended Talalay latex) with 1.5" of quilting foam over it and a high quality polyfoam base. The extra benefits of the Eurotop are listed in post #2 here.
The Natural latex model uses 100% natural Dunlop latex with wool in the quilting (which is a more costly component which adds to the ventilation, moisture regulation, and temperature control of the mattress as well as being used for the fire barrier)
You can read about some of the differences between Dunlop and Talalay in this article and post #6 here.
All of the Dreamfoam options are very good quality and value but of course each offers different options that may be more important to some and less to others.
The Sultan Laxeby is also good value IMO for those who are looking for a tension adjustable flexible slat base.
As far as the Ikea beds go I don’t really know their quality/value or their strength and I haven’t researched the materials (many of them seem to use either particle board or MDF which is stronger) At least they are very inexpensive. I would guess that they would at least be strong enough to hold the mattress and the people on it in most cases as long as the slat system was appropriate to the mattress (which the Laxeby is if you prefer a tension adjustable version over a firm slatted non flexible base).
You may want to try the mattress on a firm non flexing base (or even temporarily on the floor) before deciding on whether you would need or would even want the flexible slats because they may work either for or against you. In most cases foam mattresses (except fot those that are thinner) tend to do best on rigid non flexing slats although in some cases the tension adjustable features of the Laxeby may come in handy for fine tuning. The flexible slats would have much less effect on a thicker mattress.
Phoenix