Confused about biamping and crossovers

Biamping was very effective when audio amps ran several percent IM distortion, and 20 watts was a powerful amp. Limiting the bandwidth of the signal going through the amp helped. Also, as a secondary benefit, greater power could be achieved.

With modern amps these factors no longer exist. Biamping between a subwoofer and the main speakers is the exception, because of the cost of quality inductors of the values needed for SW crossover frequency. And SW power considerations.

Biamping, or multiamping still makes sense for pro audio applications, but that's a different story.

Active crossovers are much better but have to be matched to the speakers very carefully. Also you need an amp for each driver if they are going to be fully active. The advantage with active is that each amp sees the speaker directly and not through a crossover network, ideally the amp has been designed to work with just that speaker load. This will only be true of speakers that are designed as active from the start. Having a pair of biwire posts does not bypass the crossover, just divides it into two sections. This is a very complex subject with an extensive literature. Audio Asylum will have what you need to read.