CPU load is between 30-40 usually so I guess it's fine.
Concerning the card that yields less Sols, I think it's cuz it's the first one, and it has something to do with Xorg running on it. At least on W10 it behaved the same when I had my monitor connected to it, instead of Intel gpu. Quite a few people complained about the same issue always being with the first card.
Also I noticed that after some time I start getting
msg buffer full
Why is that, is it hurting me somehow?
This might happen if one of your GPUs crashes/gets unresponsive and stops consuming messages - so check your overclocking. I'll add the gpu-id to this message in the next version, this way it will be easier to track the unresponsive GPU.