Multiple iTunes questions

I have multiple older Mac's, with different iTunes libraries, that are synced to different iPods, and due to the nature of some of that music, the iTunes versions are vintage

So, I have ignored iTunes on my newer devices. I recently upgraded my phone and laptop, and I decided to use iTunes on both. But I had the old iPhone 5 synced to the iMac, and so the new SE is now also synced to the iMac. I've loaded many CD's into the Macbook, but from what I understand, the iPhone will only sync iTunes with one computer, so it seems I need to put the Macbook library on the iMac, right?

I tried to do that, with Thunderbolt, but the iMac iTunes doesn't see the new albums? Is there some authorization trick? I've trashed that copy and am ready to try again.

Second question is that after days of importing ~100 CD's into the Macbook iTunes, I added a dozen more last night, and they ended up in a new folder (Music), instead of in the artist folders the all the others had gone into? I didn't seem to change any import settings, so has anyone ever had that happen? And how do I keep it from happening?

Thanks for your help