The Redmi 9A supports 64 bits. There is only one model supporting 32 bits, which is the Redmi 10A.
For your reference, here are some differences between 32bits and 64bits:
1. 64-bit phones can handle more data per clock cycle, leading to smoother overall performance and better efficiency. While 32-bit phones are less capable of handling intensive tasks and large datasets;
2. 64-bit phones support larger RAM capacities, often exceeding 4 GB and up to 12 GB or more in high-end models. While 32-bit phones are limited to addressing up to 4 GB of RAM directly;
3. 64-bit phones provide better support for running multiple applications simultaneously without performance degradation.