The "woolies" tops and bottoms are definitely a thin soft base layer.
For thin base layer merino items, I also like Smartwool brand "micro weight" tops and bottoms. The Ibex woolies and the SW microweight seem about the same thickness. The Ibex woolies tops have long knit cuffs (like long johns or henleys) and raglan shoulders, while the SW ones have a little hem at the wrists and regular set in sleeves and a hemmed crew neck instead. The SW for that reason can look more like a 'regular' top and be worn over a skirt better, for example.