Performance was not a issue for me but it is noticeable that this bus is hungry for some frames.
Texture-wise, it seems to be a nightmare for repainters.
Handling is indeed very poor with the G27, and the sounds are a bit strange in comparison to the real thing (but we may expect Morphi's sound pack in a near future).
Following some of the comments, it seemed to be an unfortunate rushed Christmas release, just like OMSI 2 was. The quality is not to par with the previous great buses by Alterr, although I disliked all the sounds that came with them.
Using a 3D model from stock websites do not mean that they are not useful for gaming purposes. Actually many models are well optimized; the wonders that we see in a picture are actually provided by a powerful render. What surprises me is that stock websites usually requires models to have decent templates for further editing. Given the picture provided by @VGxT4CT1CZz, that doesn't seem to be the case.