You can find some split icons in the resources tab of this game's page here on speedrun.com
The only way to record your switch to your pc is with a capture card. You can pick them up for fairly cheap on Amazon. This is the one I've got, it's fine but there are probably better ones out there. I'm not the person to ask about that though.
Oh awesome! That's great to hear! I'm definitely looking forward to learning to run this game, I've been having a great time so far!
I'm assuming that the leaderboards for this game are largely based on the original Prime's leaderboards, so I understand why this category doesn't already exist, but would it be a possibility to add it? For people like me who are just getting into Prime through this game all the out of bounds movement and stuff is REALLY daunting, so having a separate NMG leaderboard where we can still be competitive whilst learning the ins and outs of this game's mechanics would be awesome!