If everyone switched to EV cars there would surely be fewer emissions from motors but that would not be the only issue. One is the mining of metals for batteries and the cars themselves. That process, along with shipping parts around produces greenhouse gasses and environmental harm. Then consider that we are not removing carbon nor does EV cars combat the largest sources of greenhouse gases like coal/ natural gas, textile manufacturing, concrete, shipping, and beef. Additionally, the EVs need electricity to charge and if everyone on earth today switched to EVcars many of those would end up being powered by the coal power plants (although it would be a more efficient use of fossil fuel).
Electric vehicles are great and should be used. They do come with their own set of environmental problems to consider. It also worth noting that production and consumption of vehicles and everything else on the planet needs to slow. We simply have too many people doing too much. So if you have an old gas powered car that still runs, don’t throw it out to buy a new EV.
Yes about methane and also that forests get cut down to make space for pasture.