For a FVWM/Motif based theme, you may like the OL/Motif themes from B00merang.
OpenLook https://b00merang.weebly.com/solaris-8.html
Motif https://b00merang.weebly.com/solaris-9.html
The Solaris 9 theme works great with FVWM.
OpenLook https://b00merang.weebly.com/solaris-8.html
Motif https://b00merang.weebly.com/solaris-9.html
The Solaris 9 theme works great with FVWM.
For Qt-apps I use the "Windows" style so they fit together nicely.
Comparing Memphis and Chicago, there are some layout-bugs in Memphis, but I feel like it's overall a bit better balanced than Chicago.
I think all new themes are too bright and flat, Windows 9X was perfect (at least in that regard).