Great app and great expansion! I live and fly in the middle parts of Finland (Oulu - Ylivieska - Rautavaara - Pudasjärvi - region) and I have noticed that here windy gets the wind rigth most of the time and also the high clouds. With the Cumulus its not that accurate. With thermal height it is quite optimistic. Many times eventually day gets as high as windy promises but many times windy forecasts +2000m amsl already for morning / noon but in reality thermals might start to work in the afternoon. It feels that windy forecasts every sunny day +2000m heights for the thermals.
I have been comparing different models (ECMWF to ICON-EU) for the wind and different levels of clouds but so far I can only say there is some variation (of course).