Only older Leopard 2 models have ammo in the hull, near the driver, but in newer variants everything is inside the bustle as it's much safer for the crew. 99A's design philosophy comes straight from T-72 and so does it's autloader even if slightly improved.
As far we know Type-15 is only tank in PLA what has any side armor added and it also has bustle loader with(?) blowout panels. Probably giving crew better chanches of surviving than 99A.
Most of the ammo is still in the hull for NATO tanks except for the M1 Abrams. This is partially why Germans are investing a lot in insensitive propellants and explosives. The DM-73's propellant is seriously impressive with its total insensitivity to even shaped charge jets for example. The biggest problem for Russian tanks is that they store ammo all over the place. Which makes it hard to
not hit them.
This is really bad. The only worse one is likely the Challenger 2. With the recent T-90s, they tidied it up a bit, even moving some to a blow-off compartment in the bustle.
But it is still not optimal. I would not want any ammo in the fighting compartment if possible. Only the Abrams and the Type-15 can fit that requirement as of 2023. I think the time to replace the Type-99A has come.
The Abrams has difficulty penetrating its own armour with its own gun, which says quite a bit about its performance against other tanks whose guns are not superior to the Abrams'. Unless the 99A has significantly improved engineering in its gun, it likely won't perform very well against the Abrams. But again, these tanks are unlikely to ever face each other due to geographical constraints.
IMO Abrams is a very good tank with the exceptions of its weight and fuel consumption. However I still find it funny how Americans on the internet were defending its every design feature like a religion and then we learned it will become a tank with an unmanned turret, autoloader, and a diesel engine. Most religiously defended features were discarded by the US Army.