relationship between frequency and signal strength
No, your understanding is not correct.

First, just "signal strength" by itself is meaningless.  Signal strength where?  If you mean at some distant receiver, then yes, frequency is one factor in how strongly a station is received at the same distance and transmitter power.  However, there are many such factors and the relationship with frequency is not monotonic.  The difference between 93 MHz and 94 MHz will be irrelevant in a practical sense.

Long wavelengths, like are used by commerical AM (around 1 MHz) are long enough that they refract around the earth to some extent.  This doesn't really happen at commercial FM frequencies (around 100 MHz).  Different wavelengths also get absorbed, passed, or bounce off of layers in the atmosphere.  There is much more to this than lower frequencies magically have more "signal strength", whatever that actually means.