6th Rule (Float Operations over Vector Operations) is outdated:
Use the new Unity.Mathematics package and it's float3 and float4 types instead of Vector3 (Vector3 and float3 are interoperable btw so it's easy to just convert the critical code)
Even if you are not using jobs and burst, you will gain from it, it was written for performance (including all the utility methods in the lowercase math class) and it's even more convenient : you can do f.x = 5 or even f.yzx = p.xyz
But if you use burst and jobs (even if you just run a job on the main thread with .Run() ), you will get the benefits of optimized low level code with intrinsics for the math functions.
And the craziest, is that if you use float4, even if you just need xyz and always have w set to 0, you will get vectorized code ( = multiple operations at once in the cpu).