Yeah war only possible if India attacks or invades into Aksai Chin. If India invades buffer areas, only slight escalation but doubt there'd be war. If India only insists on remaining in their last few positions that they have not disengaged from, well this is the current situation and China's approach seems to be one of patience. It's already secured two buffer deals out of India but to remove India completely, it seems to have made moves with bilateral talks with Bhutan and putting pressure on Modi government through releasing photos and videos of clash probably in the hopes that Modi exchanges Indian positions for a stop to political embarrassment and supplying Modi's opposition with material.
A war is simply a massive waste of resources, lives, and time. India hasn't managed to secure the 20% or access Aksai Chin. It has lost patrol rights to two sections of the 20%. The trend favours China but to secure Aksai Chin, China must get a total buffer over the 20% (or control it) not the current partial buffer. However a partial buffer is much better than none at all and IA outnumber PLA by many times. IA can throw much more weight in manpower over this region. A long terms PLA occupation of various parts of that 20% is near impossible because if PLA number in the hundreds, IA can send 10K to push PLA out if we go back to none buffer conditions and occupation and human wave attack cycle. PLA did well the first time because the Indians did not know how it would go down. If they want to repeat June fight scenario I reckon advantage would thoroughly be on India's side.
It is very lucky and good for China that it secured buffer deal for those two sites otherwise India could simply send 100x more and actually push PLA out and take over those areas.
Knowing this, it is very unsurprising that India refuses to vacate remaining position after the latest negotiation. They have the advantage now and they know it. If PLA escalates using force, it would allow India to break buffer agreement and they may actually be able to use sheer size to occupy the 20%.
Therefore China uses alternative means to try and get IA out of the remaining positions IA are holding. These include those two general indications of strategic direction we see - pressure Modi gov and hold bilateral deals with Bhutan. Actually I'm still convinced Bhutan is thoroughly Indian controlled and aligned. MOUs are a bit worthless and China shouldn't have revealed its hand there. India is going to immediately rush to do talks with Bhutan. Putting pressure on Modi gov by giving opposition more material to unseat Modi is sort of a pointless thing ultimately since opposition will hold the same positions if in power. Only the dynamics of negotiations may change. This is BJP's ultimate counter to China's move on this - tell China that Congress would not leave positions either.
Human wave tactics has its limitations. There are many ways to counter it without resorting to also doing massive built up on your side.
1. All weather monitoring. This allow the Chinese side to know when troop movements are happening.
2. Infrastructure building near the neutral zone. This is already going apace. More will come.
3. Stop the Indians from building infrastructure inside the neutral zone.
4. Provide armor and combat weapons. If the Chinese side has a hundred people and the Indian side has 2000, in hand to hand combat, if you have proper armor and have a good formation, you can still win because the contact point is limited. When the frontline collapses on the Indian side, it usually trigger panic and they run. The next phase will be mechanized armor and mechanized cold weapons. You can even drop rocks from drones, the possibilities are limitless.
5. Psych Opt. After confrontation and getting beaten each time, and the stories of soldiers getting injured spreads, the Indian Army will be conditioned to run away instead of fighting. You can have ten thousand people, but if they run at the first contact, it does them no good.
6. Other non lethal weapons such as microwaves. It sounds like they are already deployed.
Also since they are soldiers for life, most of the Indian soldiers are too out of shape and old to be of any use up in the mountains. This will, in the longer run, drag them down economically and delay or stop their economic development. It will also allow the PLA to learn and find smarter ways to fight this type of warfare which might be useful in certain types of future encounters with a different country.