wider tires don't necessarily help with launch traction as it spreads its weight across...
Depends on the context. With respect to the stock G70 tire setup, going larger would mostly benefit power handling... or more accurately, transfer of drive
wheel torque to the road surface. This is very relevant to the guys that have souped up their engine HP/TQ substantially. If you're pushing 500+HP, going wider than stock could quite possibly help with that torque transfer.
That said, launch traction is governed by far more than tire width. One big determinant is tire compliance. A lot of guys probably can't quite put a handle on the concept of tire compliance, so here is an extreme example to illustrate:
https://packaged-media.redd.it/8d0s...=5a945b6dac2084a76baf5d49ae0d4e6572eb654f#t=0
So does this mean you need these drag tires on your G70? Unless you turn yours into a top fuel dragster... of course not. What this does help explain is why some guys complain about going to very wide and low-profile rear tires and still struggle on launch. The problem is compliance... or the lack of it. By going to very low-profile tires, you reduce tire compliance to almost nil. Your rear tires becomes so stiff, they have a tough time "biting" the road surface. Even with LSD, the two rear tires could take turns bouncing off pavement & breaking traction, swapping torque side to side.
The way to prevent this is switch to a rear
wheel as small in diameter as would fit over the brakes, and limit the width of rear wheels to the narrowest that is recommended for the tire size you need to handle your car's HP output. By doing so, you maximize tire compliance for optimum launch traction.
a larger rectangular contact patch.
More rectangular contact patch as you go wider, yes. Larger... not necessarily.
They do help with lateral traction though.
Yes, but up to a point. It mainly has to do with load sensitivity. That is a long dissertation, so I'll let Jason explain it:
Beyond that, there are other nuances that are worth considering. One aspect is how wider tires affect handling and chassis balance. This is more relevant to those of us who prefer track days to the 1/4-mile. But it applies to the road as well. Again, I'll let this video explain it, with actual test results: