Do I lose quality compared with exporting from Insta360 Studio?

No. People export from Insta360 Studio in ProRes for two reasons: the footage is not compressed a second time before editing, and it keeps 10 bits. Two Left Wheels 360 gives you both without the export. Your editor receives uncompressed stitched frames made straight from the camera file, in 10 bits when the camera recorded 10 bits, so your final render is the only compression step.

You also skip what ProRes costs: the wait for the export, and files of hundreds of gigabytes per hour of 8K footage that you either keep or export again when you return to the edit.

An H.264 or H.265 export, by contrast, compresses the footage once before editing and again when you render, so detail is lost twice.