Hi SeekingSoundSleep,
All three of these would provide suitable and even support under a latex mattress but you will need a bedframe that is the right height for you with good center support to the floor and that will fit them because they aren’t stand alone products. While Ikea has bedframes that fit them … they have a metal bar in the center but no center support leg underneath them so I would be cautious using them with a heavy latex mattress. The Luroy and the Laxeby are both flexible slat foundations that can change how your mattress feels and performs so in actual experience they may work better or not as well as a rigid slatted foundation depending on how the combination works for you but the recommendations for your layers would be based on a non flexing support system. If you sleep in the middle of your mattress where there isn’t any flex in the Laxeby or the Luroy then this part of your sleeping surface may feel firmer for some people than each side. The Lade is just a set of wooden slats that would also need to be used on a suitable bedframe but it would be closest to the feel of a slatted non flexing foundation. I don’t know the strength of the wood they use (they don’t say what type of wood it is) so I don’t know its bending strength but I believe it has 15 1" x 3" slats (which would be .75" x 2.5") and this would mean that the gaps between the slats would be less than 3" so it would be fine.
There is more information about foundations and other types of support systems for different types of mattresses with some specific suggestions for which types would be suitable for an all latex mattress in the foundation post here.
Phoenix