Honestly I’m not sure. I believe 2.4.8 is actually Pixhawk1 v2.4.8, as discussed here:
I would assume then that 2.4.6 should be Pixhawk1 v2.4.6, but the link you provided says it’s also known as the Pixhawk2. That being said, the whole Pixhawk numbering scheme is/was something of a mess, so it’s possible that they’re the same thing. Given BR staff on the forum have previously said that the 2.4.6 should work then I would expect that to be the case.
At the moment using the Pixhawk 4 requires using the development version of ArduSub. If the 2.4.6 is actually a type of Pixhawk 1 then the normal (stable) ArduSub firmware is probably fine, but otherwise there may be some minor integration issues that we would need to help fix, like with the Pixhawk 4.