I can't find a benchmark for chacha20 as a PRNG (I've only found benchmarks for salsa20...). Why don't you try the code from [1] and see how it compares to your chacha20 random number generator?

I have done such a benchmark when implementing my cryptographic library: https://monocypher.org/speed

Also look at BearSSL: https://www.bearssl.org/constanttime.html 2.4GB per second for AES-INI is comparable to my own measurements with AVS-256 Chacha20.

Chacha is slightly faster than Salsa, mostly because it removed some word shuffling Salsa needed for matrix transposition.