My home is 100% electric baseboard heat, 220, and is 27 years old.

I live in West Virginia, elevation 2,000 ft, cold winters, warm summers.

I save electricity by only heating rooms needed so in general I am happy.

Question is - Are there newer models (perhaps fluid filled) that are more efficient where it might pay for me to replace some of the 27 years old units with newer more efficient units?

Since thermostats are in each room and each room has 220v it would be easy to replace, just not sure if I really gain anything of significance?

Question is - Are there newer models (perhaps fluid filled) that are more efficient where it might pay for me to replace some of the 27 years old units with newer more efficient units?

All electric heat is 100% efficient no matter what type you use. There are some brands that advertise they are better than regular electric baseboard heaters but that is bunk. The fluid type heaters maintain a little bit better control over the release of the warmth from the heater but that is all.
So the answer to your question is Keep What You Have.

Unless you have a failure of one of your thermostats Keep Them Also.