Is it possible to shrink the testes and penis but largely not affect sex drive? And if it is, what is the best way of achieving it?

Some medical drugs can have the effect of lensing erections. With in time the penis may shrink some. That would be a side effect. You may not like primary effects or purpose of the drugs.

Think most things that will make the balls shrink would also have effects on hormone production. That would effect sex drive.

Thanks Bobbie

Yes, there's always off-label uses for drugs. That's how Finasteride got going for treating male pattern hair loss. It started off as "Proscar" by Merk for treating BPH "Benign Prostatic Hyperplasia" in reducing DHT levels in the prostate, and they noticed many patients were experiencing hair growth where they had been previously thinning.

But I'm sure the drugs you're alluding to are for conditions that may potentially cause some serious side effects.