Correct. The LFE (sub) channel is a discrete channel with content mixed 120hz and below.

The LFE setting and speaker crossover setting are two different things.

The crossover point for other channels is not related to the LFE in the way you state unless you use LFE+Main where bass content below the crossover point in the “small” channels is mirrored to the LFE and L/R channels.

You should NOT use LFE+Main if you care about system headroom in your amplifier. Time aligning your mains to subs and group delay will also be less ideal. -But a good idea if spl quantity is the goal for sure.