Hi matthewsoft,
Most of your questions are answered in the tutorial post here which is where I would start your research and has all the basic information, steps, and guidelines that can help you make the best possible and most suitable choice … and know how to avoid the worst ones.
Most “all latex” mattresses do best on a rigid non flexing slatted foundation with gaps that are less than 3" in between the slats but the Laxeby can also be a suitable choice as long as it fits your bedframe, is high enough for you, has good center support to the floor underneath it, and in combination with your mattress provides you with good PPP. It has the advantage of being able to fine tune the support under your mattress in different zones to improve alignment or pressure relief as long as your mattress isn’t so thick that the adjustable zones would make little difference you can feel or notice in “real life”. There is more about the types of foundations that are usually used in combination with different types of mattresses in the foundation post here and the two posts that are linked in the second paragraph.
You can read more about the differences between a latex/polyfoam hybrid and an all latex mattress in post #2 here.
Probably not because dust mites need a source of food (usually skin particles) and higher humidity. You can also use a dust mite encasement to control dust mites in any mattress, box spring, or foundation. There is more about controlling dust mites in post #2 here.
You can read more about hotel mattresses in post #3 here and the posts it links to. In general I would avoid them or any mattress where you aren’t able to find out the information you need about what is inside your mattress. One layer of latex in between lower quality materials really won’t make much difference and a thick pillowtop that has lower density foams in the upper layers is a very risky purchase in terms of durability. Hotel mattresses are also more costly and generally lower quality than an equivalent consumer mattress made by the same manufacturer (Simmons in this case).
Phoenix