Hola Marcos

Sorry, this went through the cracks.

I think the relevant thing here would be to notice that an adverb can modify both a verb and an adjective. So you have these different uses of them in different sentences depending on what they're modifying. It's also good to remember that adverbs are invariable so they don't need to agree with anything, they use one single form. (demasiado, tanto, mucho, poco)

So, when we use the adverb "mucho" (in this case only used to modify a verb, not another adjective, as you highlight on your comment) is always going to be "mucho" (not mucha, muchos, etc) 

Your comment on "tanto" as being a direct object, bear in mind that it can only be a direct object if that was used as a pronoun. So, if I say for example:  "He comprado un pollo, solo para mí, y ahora creo que no debería haber comido tanto." - Here, this can be interpreted as a pronoun (referring to "tanto [pollo, so much of "it"], so I believe its function in the sentence would be a direct object. However, if you are simply saying "No debería haber comido tanto" (without a referent), this would be an adverb modifying the verb comer (adverbio de cantidad/quantitative adverbs). 

So, to summarise, I think being aware about this helps us understand the grammar and the language better. 

I'm not sure if this is what you were referring to when you asked "Are the different types of adverbs significant?"

Saludos cordiales