Also should add that you will read everywhere people claiming that those Leclercs, M1s, and Leopard 2s destroyed in the middle east in the last few years are all due to selling them sub-standard variants. These claims are garbage and come from the mouths of western stronkists who cannot take the ego hit. The truth is these sold tanks are nearly identical in armour package with the main difference being some sensors, electronics, software, and communication equipment. The mechanics are exactly the same because the production line will not be redeveloping an entirely new method of fabrication and manufacturing of parts just to sell another nation a monkey model. It will cost the seller far more. On top of this, the buying nation spends about three to four times the cost to buy a unit compared to the manufacturing nation. Sure this includes some parts and support, but they are paying serious coin for each tank. They have experts evaluating the tanks, checking them, and keeping an eye on the production facilities. These are tanks we're talking about, not turbofan manufacturing.
So in summary, the ideal side armour is one that is modular and can be modified to meet dynamic requirements of the battlefield and future weapons. One that withstands the common RPGs and small arms (can defeat using APS as well but that's usually cost ineffective), basically the lower threat category munitions that have high possibility of outflanking the tanks, any more side armour is dead weight until it is able to defeat the main anti-tank munitions, making it almost as thick and heavy as frontal arc. And frontal arc can be penetrated. Welded turrets with composite ceramic plate armour is OLD news... the whole thing is a science and defeating it once you know the composition is easy work. Expect latest generation of anti-tank missiles to be effective. Russian and Chinese sabot rounds are less capable than NATO ones owing to the two piece ammunition requirement from auto-loader, rather from the Soviet desgin carousel autoloader, resulting in shorter sabot rounds.