Cast wheels are just poured into a mold. 3 piece wheels are forged, meaning they were beat to shit to get the shape they have. Think of it as a sword.
When it comes to cast wheels though, there are different materials used. While a replica of a 3 piece wheel is weaker, a replica of a monoblock wheel is not necesserily weaker. It's already clear that forging is stronger than casting, so we got the 3 piece out of the way. Monoblocks differ in quality due to the materials used. A replica's strength can be compared and even SOMETIMES be stronger than the original, but because of the casting method used you will have a WAY heavier wheel. Even if the replica is stronger than the original it doesn't change the fact that it's a copied (liscensed) design from the more performant (in many cases lighter) original.
Then you take a look at this.
http://www.mirowheels.com/product.html
You recognize some wheels in there. STP1 - WRD Chevlon, STP3 - OZ Mito, 279 - BBS LM, 942 - M3 wheels. The 3 piece replicas are obviously cheaper, they weren't forged. They are 2 piece cast wheels that are not meant to be taken apart after initial assembly, hence the name; fake splits. You might notice that some of those aren't copied from another company. While the design might be original, they are still 2 piece cast wheels pretending to be a 3 piece. So they are not exactly replicas but are still fake splits. If you look at type 942s however, you'll notice they are a monoblock cast wheel. What kind of casting did they go through compared to the originals? What materials did they use exactly? We won't know unless you actually test them. Performance aside, they are still replicas.
My wheels for example aren't forged, they're cast. Are they weaker than 3 piece forged wheels? Yes. Stronger or more performant than other replicas? Who knows, I didn't do any tests. Big + of my wheels? Exclusive design with huge rep back in my country (they're apparently played in Europe). Also, I know they're beast fucks.
In any case, designating every kind of replica or fake split is a headache. We just put them all in the same basket, fake wheels/replicas.