V27 aka V2018 and earlier V26 aka V2016 both work quite well. Quite a few new features over the years, and unless you look really hard, you probably won't notice many changes to what was there before. This in itself is amazing. The redSDK renderer was a big part what was new in these versions.
The programming team ie developers were changed at the end of the V2018 cycle, and the last update finally kills off the unfortunately unsuccessful RedSDK 3D Rendering implementation.
V28 aka V2019 has been out for a while with a couple of serious bugs, the patch which seems very imminent now appears to have fixed those. It has 2D pdf import built in which some will find very handy. Also some export formats related to 3D printing.
They are now starting work on V2020 we have no idea what will be new in that. We are hoping for improvements in the area of rendering and shadows.