Looking at the user manual for G7X III, it appears to have both automatic (TTL) flash mode, and a manual mode which, I presume, won't fire a pre-flash and remove the associated shutter lag - a marked advantage over Sony cameras where the pop-up flash always functions in TTL mode.
If by 'Are Canon cameras with TTLs dead?' you're referring to the presence of a hot shoe as an alternative to the pop-up flash, smaller compacts haven't had a hot shoe for a while now - land shooters simply don't use tiny cameras with flashes that are several times larger than the camera body, and underwater photographers are a tiny market. Larger compacts such as Canon G1X III, Panasonic LX10 II and LX100 II, Fujifilm X100F still have it. Even so, underwater, most people prefer optical triggering over electric sync due to fiber optics removing two to four potential water ingress points, and the cables being much less bulky. LED triggers really give you the best of both worlds, but represent several hundred dollars in additional costs, and require a hot shoe to attach to.
Video lights can be used for stills in some situations, but strobes are massively more powerful - tests indicate that it will take an approximately 1 million lumen light at 1/60s to match the output of a Sea & Sea YS-D2. Compact LEDs with that much power aren't going to be available anytime soon.