I would suggest rendering caustics as separate pass that's 100perc. denoised. Btw AI denoising (Optix) does pretty cool conversion of caustics because the artifacts it produces sort of just look like more detailed caustics :- ).
I would even go one step further and render it as separate simplified scene (ultra simplified, only to produce caustics in best way and nothing else), and render that with Optix denoising, that way you don't even need many passes at all.
This setup is more laborous but you will get super clean caustics at fraction of time.