A pipeline with GPU Effects and most CPU filters with 8-bit export will go like:
10-bit YUV Rec. 709 color → 16-bit float linear color → usually 8- or 10-bit RGB(A) sRGB color, could also be YUV 4:2:2 Rec. 709
Rec. 709 in the above is for example, could be other common color spaces such as 601 or 2020.
But there are new exceptions described here:
Is there a list of filters to avoid?
Nearly all except the list in the linked reply, and you need to add mlt_image_format=yuv420p10 or mlt_image_format=yuv444p10 to Export > Other because it and most presets (except the ten_bit category) default to 8-bit. mlt_image_format determines how the images are requested from the pipeline, but pix_fmt determines how the encoder will export. A filter will try to give what was requested, but if it cannot will fall back to something else it chooses. You can ignore the parts about colorspace and color_trc because that gets into HDR. (What I describe in the linked reply is a form of crude HDR edit support where images are primarily passed from the decoder to the encoder.)
In the next version of Shotcut there are new keywords added to the filter descriptions, and you will be able to search for #10bit.
regarding LUT3D. When I add it at the point it should be i e. after CC, it instantly gives me back banded
LUT3D has the #rgba #10bit keyword because it can do >8-bit RGB pixel formats. Keep in mind that the Shotcut preview always asks the pipeline for 8-bit because that is all it knows how to handle and is much more efficient (less data transfer). However, with mlt_image_format=yuv444p10 I can see in the export job log that lut3d is using fmt:gbrp10le. Good!
GPU setting has some form of colour management?
Yes, it converts to and from linear color. It handles SDR color spaces and gammas but not HDR transfer functions.