I use either index on the B key depending on what makes the most sense in the moment. You can't be putting a key in the exact middle and then split the keyboard and just give it to one side. What kind of shit is that I'm not playing your B key on whatever fucking hand you think should be B key game homie!
Besides a regular keyboard with a nice wrist rest and I'm fine. I keep my wrists pretty straight which maybe doesn't put me in the best pure speed typing position but you know what? It's fine. Little to no strain. And when I am doing some good ol' fashioned FPS I angle the keyboard a good amount so I'm WASDing straight on.
I think I had an 'ergonomic' keyboard from Microsoft 20+ years ago and I hated it. I see on Amazon that there are keyboards nowadays that are split but you can basically connect them into a normal keyboard. That's the kind of anti-split keyboard hedging that I would go with were I to try the concept again.