Advice on basic setup

Good to hear that you've gotten started! Did you set up security yet? That's the very first thing I would recommend.

Aside from that, you don't need to keep separate sites on separate disk images, keep them together unless you have a specific plan to keep it modular (or whatever word would fit this idea best).

For now, your set up sounds right as long as you have security set up. Additionally, do you have SSL enabled? If not, you can get free certs with Let's Encypt. Set that up for some additional security and trust.

Good luck!

I usually suggest to avoid using multiple disk images on the same linode. If you don't plan your space properly, you end up filling up one disk while wasting empty space on another disk.

There are cases that require multiple disks, like when you share them around multiple systems, or when you need the flexibility of hot-swapping them with new data, that sort of thing. But in most cases you don't need multiple disks.