I take it you want to use the ASIO support from VoiceMeeter and maybe have some extra monitor. control? Can you tell me what is hooked up to your PC's Speaker output and what is hooked up to your Line Out if anything? That makes it easier for me to explain the following.
But going by what you have here, you don't have to set VoiceMeeter as any default device in Windows. If your sound making program and/or sound recording program can change (virtual) hardware then it will work without having to change it. Right now, VoiceMeeter is set to record ALL of your Windows sounds including games, browser, etc. over . If this is not what you want I suggest putting your default output back on "Speakers" or "Line Out". I would actually recommend it as VoiceMeeter itself outputs over your A device which is your "Focusrite" thing. Also, your output format does not matter so you can leave that on whatever you want.
What's happening in your set up is that you are bypassing VoiceMeeter. You are recording the input to VoiceMeeter rather than VoiceMeeter's output. VoiceMeeter's output which is similar to any external device such as Line-in, Mic, etc. In OBS you'll need to use the correct input so that would be any Mic/Auxiliary Audio Device.
Just note that if you send the output coming from the virtual input to the Speakers (channel A1 in VoiceMeeter) and the Speakers are selected as the Desktop Audio Device in OBS people watching your stream will hear it twice. You could set A1 to your Line Out if you have something on there like headphones or something.
I've added a picture of the set up. Red are connections that happen virtual and automatically. Blue are internal connections and green is what connections you have to set up.
Connection A (on the right) is only useful if VoiceMeeter's A1 output does not go to your speakers but you still want OBS to record Ableton like on the picture. In this picture you have your final Ableton not go through Windows' output but straight to your Line Out, as an example I'm just gonna call that Line Out device your actual monitoring hardware.
But I would really just recommend sending A1 to your Speakers and then have that as as Desktop Audio in OBS and then you can forget Connection A and OBS' Mic/Auxiliary Audio Device all together. The only reason I could think of to run a separate audio connection from Ableton directly to OBS without Windows' desktop and games sound on it is when you would like to watch YouTube videos in private with your viewers only being able to hear Ableton (obviously you could disable the Desktop Audio in OBS entirely then or just mute it in OBS' audio mixer).
I hope I explained it well enough, it's kinda late here and I got side-tracked at some point. Just let me know when you have more questions ^^