I should probably split this topic, as we have gone a little off the original subject...
Playmobil added construction elements and buildings to a figure system, in the same way that Lego added figures to a construction system, so there are elements of figures and construction in each.
For my money the Playmobil figures beat the Lego figures all ends up, and I didn't really enjoy the building part of Lego much to begin with, so my money has stayed with Playmobil. Meccano has also added figures, and I only saw a Meccano figure a few weeks ago for the first time, though they may have been around for years.
Any play system which has been around as long as Playmobil, Meccano or Lego, has naturally broadened its horizons enough to encompass many different styles of play.
In Playmobil's case the Steck and System X pieces allow and encourage adaption, extension, and modification, but there are still many sets that have no building parts at all, but still provide good play potential. I don't see these as an optional add-on to a building system, rather the buildings are an optional add-on to a figure system.
I came to the Playmobil world (or rather it came to me) in the ear before buildings, and have collected occasional sets over the ears, but not until last year did I possess a single set with a building piece. That was a small pirates dungeon, and not enough to build more than a tiny tower - though it certinly made the set more expensive.
Since then I've added a LOT of castle sets, which by their modular design can be used to construct different castles, and a few Western and Medieval buildings which are stand-alone structures with no obvious "construction" options.
There's a difference between construction and assembly.
btw, now I've seen those Sylvanian family buildings, I'm goig to check out the scale, if it's close enough they might be useful. There's a great windmill, and I don't think PM have done a full windmill in the European style that you can live inside. Now see what you've done! You have spawned a monster!