Performance benchmarks between mongodb versions

Hi everyone,
Our project has been using MongoDB v3.2.10 for a long time and wants to introduce transactions, so we are evaluating to upgrade the version of MongoDB.
We are very concerned about the time it takes to write and query data, so we did some testing. The client uses c-driver, and the compared mongod versions are v3.2.10, v4.0.28, v4.2.24, v4.4.23, and v5. 0.19, v6.0.8, unfortunately in our tests, the newer the version, the higher the write and query time consumption. I don’t know if there is an official benchmark test, and if so, what are the results?
We also found the mongo-perf tool and tested it using a similar method as mentioned on this page MongoDB Benchmark 3.4 vs 4.4 vs 5.0 vs 6.0 | by Yicheng Zhou | SerpApi | Medium, with almost the same results, v6.0.8 achieves impressive query performance improvements, but if we use the c-driver for testing, v6.0.8 is the one that takes the most time and it confuses me, can anyone help? sincere thanks.