I suspect the quantizer plugin insert is no longer maintained, i.e., you don’t get as many quantization choices there as you do in the quantize panel. It takes even more mouse clicks to get to the quantize plugin settings in the inserts menu (which uses an excruciating small font with up/down arrow to change it).
The quantize plugin setting applies to the entire track. You can keep that plugin open in the MIDI inserts section such that when you switch from track to track, the quantize plugin will display (or recall) what the current quantization setting is for each track. That’s the only place I know of where Cubase actually recalls and displays what MIDI data has already been quantized to. It would be more useful to recall and see what quantization is already set to on a finer per MIDI region basis instead of a per track basis. Newer DAWs do this automatically in their inspector panels for MIDI data/regions. Cubase is an older design that does not provide that kind of region based inspectors. (I added a feature request for it anyway, Display and set quantization parameters per MIDI region (regardless of track))