I guess the free version will have limited render resolution but they are a feature of the camera and it's basically a checkbox you need to set, nothing else. TG aves high dynamic images to EXR, which is similar to HDR, so no problem here.
A personal note - I'm also doing aviation related stuff and rely on TG for exactly this purpose, spherical environments and sometimes backplates. TG has a a very natural sky model and beautiful clouds. Give the free version a go and decide for yourself!