What's the difference between prenasalized voced plosive /ᵐb/ and just the sound /mb/, if any? I've watched this video where /ᵐbʷ/ is pronounced, and I'd pronounce /mbʷ/ in the same way.
There is no phonetic difference, but there is also no phonetic unity supposed ᵐb / mb are pronounced in many different ways across languages. On occasion, there is an audible contrast between two such things, which is usually based on some durational facts, with the nasal being of different durations. Swahili and Sinhalese are examples of languages with two such types of NC. There are also languages where physical what sounds like [m] versus [mb] is related to the timing of the raising of the velum, e.g. in Guarani, and other languages where you find [m] before nasal vowels and [mb] before oral vowels. Phonologically speaking, the implication of the term "prenasalized" consonant is that is is a special kind of single consonant, which has a brief initial nasal period. In Swahili and Sinhalese, these are consonant clusters with different prosodic properties associated with the individual elements. So from the phonological perspective, "prenasalized" consonant means "single segment with two specifications of nasality".
I don't recommend watching random Youtube video of anonymous performers, performing what they think something is supposed to sound like. Instead, you should learn from exposure to real languages. I am aware of the lacuna of learning materials. So for example focusing on contrasting examples in Swahili, Sinhalese or Guarani... except, these are not languages with masses of good-quality listening materials. The number of language with arguable "prenasalized" consonants is near zero. The problem is that people often just assert that apparent mb is a prenasalized consonant if a syllable can start with that sequence, because it seems strange (to some) to allow nasal followed by stop in the onset of a syllable.