It seems unlikely to me they're using floats in inner-loop calculations. Floats are significantly slower than integers in general. Rather as much as possible you try to use tricks to turn everything into integer multiplication if possible. Such as fixed-point arithmetic. You can always convert to/from your internal representation before/after you start the nitty gritty calculations. As that only happens once.

But as to whether 32 or 64 bit int is much different, that would absolutely take benchmarking as there's a large number of factors in the complexity of an x86 cpu as performance could easily be determined by branch-prediction-failures or cache-misses (at varying levels - incidentally another reason besides SIMD to prefer 32 bits as the storage state - takes less CPU cache space!) moreso than how many multiplications per second could be done with perfect utilization using AVX registers vs normal registers.

IF it came down to the number of mathematical operations per second being the critical issue, AVX (which CAN do twice as many multiplications in 32 bit mode vs 64 bit mode) should be faster for doing large numbers of independent operations in parallel, as that's its entire reason for existence. BUT I think there's an overhead to packing/unpacking AVX registers when the data may be coming from different locations - it's intended to be taking a large continuous bulk of data with many many discrete pieces being treated the same way - so it might be taking a significant overhead hit that it has to pay for before it can pull ahead.

Bottom line is they'd need to benchmark alternative implementations to see how much of a performance gain/hit they take from different approaches and whether or not that's "worth it" for other tradeoffs the approaches might bring with them. It is extremely difficult to predict what optimizations are important with all the moving parts inside a modern CPU's architecture - which is why among other things it's recommended these days to not think too much about optimization until you've got a functional implementation and have a profiler tell you where it's using its time.