One compound even in a moderate amount by itself will do the job adequately.
Both are serms, yes they are different chemical compounds. Clomid, is a fertility drug that stimulates ovulation in women, and testicular activity in men. Nolva was originally intended for treating breast cancer by regulating the bodies ability to absorb large amounts of estrogen if it is present in the system. I don’t really know the mechanism that nolva uses, but it works as a PCT drug.
Either high amounts of one serm, or doubling up on the total amount of serm can be counter productive. Apart from being an overkill, you can develop side effects.
Some people don’t like the effect of clomid, makes them weepy and emotional and unstable Probably due to taking too much. It can also effect your vision.
Add to all this that you will be taking hcg on cycle your balls have been getting stimulation on cycle, pct shouldn’t need large amounts to get you back to normal after your cycle.