There is no smaller cache. L1 and L2 are the same capacity (but smaller area) for Zen 4 and Zen 4c: 32kB and 1MB respectively. The L3 cache is 16MB for Phoenix and Phoenix 2, so it's actually more L3 per core for the 2+4-core Phoenix 2 than the 8-core Phoenix. It's only in the server Zen 4c processors (Bergamo) that they've cut L3 per CCX in half.
The only heterogeneity experienced by software will be due to the lower maximum clocks on the Zen 4c cores, which is a far simpler problem to deal with than Intel's P vs E cores or AMD's 7950X3D with 3D V-Cache on only one of the two CPU chiplets.
Performance per clock has already been verified as the same: https://pic2.zhimg.com/v2-866cc994355fb54831c7398c97b20479_b...
The only heterogeneity experienced by software will be due to the lower maximum clocks on the Zen 4c cores, which is a far simpler problem to deal with than Intel's P vs E cores or AMD's 7950X3D with 3D V-Cache on only one of the two CPU chiplets.