FLWM is a good choice regarding memory and cpu usage, however, there are several WMs to chose from, providing possibly more or different functionality.
Nice fact about TinyCore, If an extension is not loaded, it's virtually not present. Meaning you can mess around with different window managers, ignoring what was loaded the former boot.
You can destroy your system, reboot without backup, and everything is in good shape.
In other words, do experiment; if things go wrong you know where to ask. But experimenting is the way to go. Always.