Fender “Brown Face” modulation is floating high and low harmonics. This was the Tweed or Showcase Fender amp sound. “Black Face” tremolo is what you describe, at high rate it can almost sound like on/off cycles. The Brown Face style is what you hear in a lot of the old surf rock classics.Tremolo is an AMPLITUDE modulation effect, the modulator jacks the volume up and down so unless you are going for some kinda special effect I don't see the point in rapidly having your volume go in and out unless you are trying to make your amp sound broken LOL.
Tremolo IS the sound on guitar on the old surf records and of course what made Creedence Creedence; I was in a band that played "Born on the Bayou" and could not get it through the guitar player's thick head you need TREMOLO to get that sound, he just kept futzing with a damn chorus pedal. Chorus modulates the PITCH, Tremolo modulates the amplitude, all they have in common is they both modulate the signal.
I'm a total delay freak, I own a way vintage cool Lexicon SuperPrime time in my studio F/X rack along with a Line Six Echo Pro (which emulates various classic delay devices). Even then the only use I ever found for delay on bass was a slapback kinda effect to sound like the intro to "Cygnus X1" or on a bass solo harmonics thing.
On regular bass? Just not my jam but I'm not a big fan of effects on bass.
NOW on OTHER STUFF, oh yell yeah I love effects processors which is why I have 9 of the things in my studio rack, but they rarely get used on bass tracks.
Analogeezer
Some tremolo effects are one or the other, some offer both.