A key question for the evolution of thermokarst wetlands and lakes in Arctic and sub-Arctic permafrost regions is how large-scale warming interacts with local landscape conditions in driving permafrost thaw and its spatial variability. To answer this question, which also relates to risks for ecology, society, and health, we perform systematic model simulations of various soil-permafrost cases combined with different surface-warming trends. Results show that both the prevalence and the thaw of permafrost depended strongly on local soil conditions and varied greatly with these for the same temperature conditions at the surface. Greater ice contents and depth extents, but also greater subsurface volumes thawing at depth under warming, are found for peat soils than other studied soil/rock formations. As such, more thaw-driven regime shifts in wetland/lake ecosystems, and associated releases of previously frozen carbon and pathogens, may be expected under the same surface warming for peatlands than other soil conditions. Such risks may also increase in fast permafrost thaw in mineral soils, with only small thaw-protection effects indicated in the present simulations for possible desertification enhancement of mineral soil covers.