I am seeing many of your posts here and at Cloudy Nights of the same subject. It's unclear from you about your goals, equipment you own (Eq or Az mount, etc.).
I do not recommend ZWO cameras for DSOs except for very bright DSOs. ZWO cameras are uncooled and noisy if exposed over 3 seconds. Dark, bias and flat calibration is an absolute MUST for noisy cameras. Also, it would be best to dither noisy cameras and that usually requires EQ mount, and autoguider camera.
Upgrading from ASI120MC to ASI120MC-S would be very little difference. It might make a difference for Lunar and Sun imaging because they are very bright and higher frame rate is possible from ASI120MC-S with USB 3.0 port. For planets, very little would be gained since planets are dimmer than Solar and Moon, the exposure will need to be longer which would lower the frame rate therefore USB 3.0 would be little help. You can increase frame rate imaging planets with ASI120MC by using smaller ROI which will reduce resolution and help increase download speed which also increases frame rate. Using USB 3.0 would not be much better. Frame rate is limited to brightness of target objects. The dimmer the object the greater chance to lower frame rate and USB 3.0 may not be beneficial.
Upgrading to ASI174MC may be beneficial since your scope has pretty long focal length and larger pixel camera would probably work well. But I doubt quality would be improved if you upgrade to another color camera unless you upgrade to mono version of ASI174MM and use filters. Mono camera with filters will produce greater detail because each color (RGB) would be at 100% resolution while color camera is limited by Bayer Matrix (25% Red, 25% Blue, and 50% Green).
ASI174 cameras have larger FOV which would be useful for Solar and Moon but not much useful for planets unless your focal length is over 10,000mm. ASI174MC may be not beneficial over ASI120MC/MC-S for planets because you would likely use ROI to increase frame rate and ASI120 already has enough FOV for planets for most scopes including yours.
If this was your first time buying a Solar/Lunar/Planetary camera, I would have picked ASI174MM/MC. But upgrading from color camera to another color camera may not very beneficial even if the new camera has USB 3.0 port.
Peter
