Asymmetric dual channel works: first 8+8 in dual, remainder single.

Yes, exactly — the first 8GB on each stick will pair in dual channel, and the remaining 8GB on the new 16GB stick will run single channel.

This is called “asymmetric dual channel” or Intel Flex Mode. Your laptop’s CPU will use the matching 8GB chunks in dual channel for memory-intensive tasks, then fall back to single channel when it needs the extra capacity. In practice, you’ll see a small performance hit only when you’re using more than 16GB of RAM. For most everyday work and even gaming, it’s fine. The alternative (ditching the 8GB stick for a 16GB one to get 16GB dual channel) is cleaner, but this setup gets you that extra headroom without wasting the existing RAM.

Worth doing if you need the capacity. Future You will thank Future You for not buying two sticks unnecessarily.