Current Canon Powershot G?X series models include:
G1X Mark III... 24MP, APS-C size CMOS sensor, built-in electronic viewfinder, dual pixel AF (phase detect), 9 fps, 24-72mm f/2-2.9 lens (film/full frame equiv.) ... $1100 sale price (reg. $1300).
G1X Mark II... (discontinued but widely available) 12.MP, 1.5" size CMOS sensor, separate electronic viewfinder (EVF-DC1 or EVF-CD2, using hot shoe), ? hybrid contrast detect AF ?, 5 fps, 24-120mm f/2-3.9 lens (film/FF equiv.) .... $600 sale price for G1X Mk II, $300 for EVF-DC1, $200 for EVF-DC2.
G3X... 20MP, 1" CMOS sensor, separate electronic viewfinder (EVF-DC1 or EVF-DC2, using hot shoe), "fast" AF (? hybrid contrast detect ?), 7 fps, 24-600mm f/2.8-5.6 (film/FF equiv.).... $900 sale price w/EVF-DC1 (reg. $1300).
G5X... 20MP, 1" CMOS sensor, built-in electronic viewfinder, ? contrast detect AF ?, 6 fps (4.5 fps w/continuous focus), 24-100mm f/1.8-2.8 (film/FF equiv.).... $700 sale price (reg. $800).
G7X Mark II... 20MP, 1" CMOS sensor, no viewfinder, ? contrast detect AF ?, 8 fps (5.4 fps w/continuous focus), 24-100mm f/1.8-2.8 lens (film/FF equiv.)... $650 sale price (reg. $700).
G9X Mark II... 20MP, 1" CMOS sensor, no viewfinder, ? contrast detect AF ?, 8 fps (4 fps w/continuous focus), 28-84mm f/2-4.8 lens (film/FF equiv.).... $400 sale price (reg. $530).
Note regarding AF: Latest top of the line Canon are using a Dual Pixel AF system that's phase detection and faster than earlier contrast detection methods of AF. There have also been different versions of contrast detection.... A hybrid version performs better than the standard version. Of the above, only the G1X Mark III uses DPAF. Buyers considering other models should carefully investigate AF performance.
Viewfinders.... Want a built-in electronic viewfinder: G5 or G1XIII. Optional electronic viewfinder (EVF-DC1 or EVF-DC2 mount in hot shoe): G1XII or G3. No viewfinder at all: G7II or G9II.
Flash.... All models have a small, built-in, relatively low power pop-up flash that draws power from the camera's battery. As noted above, models using a built-in viewfinder also have a hot shoe to accommodate an accessory flash. Models that rely upon an accessory viewfinder use the hot shoe to mount the EVF, so cannot be use with an accessory flash at the same time the EVF is being used. 7DII and 9DII do not have a hot shoe or any means of using a dedicated accessory flash. (Non-dedicated flash may be usable, optically triggered by the camera's built-in flash.)
Sensors: G1XIII uses larger APS-C size (same as now used in all APS-C Canon DSLRs, 1.6X "lens factor"). Earlier G1X versions use a slightly smaller 1.5X size (very close to "micro 4/3" size, 2X "lens factor"). Other G?X use slightly smaller 1" sensors (2.7X "lens factor"), but those are still considerably larger than the tiny 1/1.7", 1/2.3" and 1/2.5" used in many point 'n' shoot, non-interchangeable lens digital cameras (Lens factors: 1/1.7" = 4.7X. 1/2.3" = 5.6X. 1/2.5" = 6X.) Larger and less crowded sensors such as all the Canon G?X models use, more or less, make for less heat gain and less cross-talk between pixels. That results in lower signal to noise ratio... i.e. less noise at any given ISO... higher usable ISOs and potentially better low light image quality. Less crowded sensors also often can use larger individual pixel sites, which have the potential to capture more fine detail.
Lenses: Larger sensors limit the zoom range of lenses to some extent. In other words, one reason manufacturers use very small sensors in some of these cameras is to "leverage" more extreme zoom range and telephoto reach from reasonably compact lenses. (Due to the differences in sensor formats, all lens focal lengths are stated in "film/full frame equivalents", which is common practice with cameras of this type, to allow for comparison.) Also note differences in lens max f-stops.
Processor speed, frame rate and buffer are related items. Note that continuous frame rates are stated two ways: higher frame rate is with locked AF (One Shot mode in Canon-speak), while the lower fps is with continuous focus (AI Servo, Canon calls it).
All the above models have image stabilization, but buyers should compare the ratings and features of each. Some IS is more sophisticated and capable than others.
All the above models also have articulated, Touch Screen LCD monitors on the rear. Size and resolution may vary a little, so check the specs.
All above models can capture both JPEG and RAW image files. RAW files from all models are 14 bit.
https://www.dpreview.com/reviews/canon-powershot-g1-x-mark-iii-reviewhttps://www.dpreview.com/reviews/canon-powershot-g1-x-mark-iihttps://www.dpreview.com/products/canon/compacts/canon_g3xhttps://www.dpreview.com/products/canon/compacts/canon_g5xhttps://www.dpreview.com/products/canon/compacts/canon_g7xiihttps://www.dpreview.com/reviews/canon-powershot-g9-x-mark-ii-reviewHave fun shopping!