I don’t it will be a cake walk over India. If India can bottle up the Chinese in the Himalayas, it may be turn out to be more like the mountain war Austria-Hungary and Italy fought against each other in the First World War.
China has a long supply train through Tibet to even get to India. A war might hinge on how well their navies perform against one another. Or what Pakistan might do. China might win an air war. But operating out of those mountains might cramp both sides’ style.
I’d give the edge to India if only because they’d be fighting on interior lines in every theater and battle space. World opinion might be with India, too, if China is the perceived as the sh*t-starter. Don’t know if that would translate to material help, but they might receive some valuable intelligence.
The one big edge I’d give to the Chinese would be in cyber-warfare. If they can disrupt India’s networks and electronics, it could be the thing to turn a war in their favor. Especially if they could cripple India’s nuclear capability by it.
All just WAGing on my part. But it’s fun to speculate!
If India goes to war against Pakistan, expect India's Muslims to erupt.