Hi skyblaster,
The flexible slats of the Laxeby will provide some shock absorption under the mattress which can be important with an innerspring mattress (see post #2 here) but it will also have a different “feel” than the floor because the floor doesn’t flex at all and the Laxeby will to some degree. It will also have a different amount of flex than your box spring which can also make a difference in how it feels or performs compared to the box spring you are using now.
The Laxeby also doesn’t have any flex in the center where the slats are connected to the center beam or on the edges so it may be a little uneven under the mattress (depending on the mattress, whether you sleep in the center, and how much you would “feel” the parts that don’t flex through the mattress).
So overall I would say it would be a reasonable choice in terms of providing suitable support under your mattress and some flex and shock absorption to protect the innerspring but it won’t be as rigid as the floor so it may “feel” different.
It does have the benefit of being able to adjust the slats in certain sections so this can be helpful to firm up the center section under the heavier pelvis which may make some difference in alignment (again depending on how much of an effect this would have with your specific mattress and body type).
Phoenix