If we use ein bisschen, ein wenig, ein paar as a determiner then can I assume that the declension of adjective before noun is in a mix declension because of indefinite article ein? I write the following example with adjective rot please check if it is correct or not.
eine bisschen rote Schokolade
Examples such as the following show that if ein wenig modifies a noun, ein is uninflected and the adjective accordingly carries strong inflection.
mit ein wenig gesundem Menschenverstand
with a little bit of common sense
Note that ein wenig can also modify an adjective. This can lead to constructions beginning with ein ein or der ein.
ein ein wenig verwunderter Gast
a guest that is a little bit puzzledder ein wenig verrückte Ritter
the knight that is a little bit crazy
While ein wenig and ein bißchen stand with singular mass nouns, ein paar stands with plural nouns. Note that again ein is uninflected and the adjective carries strong inflection.
ein paar schwierige Entscheidungen
a few difficult decisions
Of course, ein Paar with a capital P means a pair and is different, as the inflected article shows (also compare Quentchen).
mit einem Paar Handschuhe
with a pair of glovesmit einem Quentchen Glück
with a modicum of luck
Finally, in colloquial speech, you can find examples such as the following, where an inflected form of the definite article is combined with bißchen or paar.
wegen dem bißchen Geld, wegen den paar Euro
With ein(e), [Bb]isschen, rot and Schokolade you can express a number of things that can vary widely in meaning:
You want to express there is a small bit of chocolate, you would use
Ein bisschen rote Schokolade
In this example, "Schokolade" has no article (that works because "Schokolade" can go as a material designation, like "Milch" or "Wasser" which can go without an article), the "ein" belongs to "bisschen".
Here, bisschen modifies the noun, denoting there is a bit of it.
You want to express the chocolate is slightly red, thus modify not the noun, but rather the adjective, you need to double the article ("ein bisschen" cannot go without an article, and "Schokolade" needs one, too because you mean a specific piece of chocolate - the slightly red one, not the material):
Eine ein bisschen rote Schokolade
If you modify the capitalization, you can modify "Bisschen" to a noun (literally meaning "a small bite") and form
Ein Bisschen rote Schokolade
like in "ein Glas kaltes Wasser"
This would not be used commonly, as it could only go for a literal bite of chocolate that someone bites off and spits out.
But after all: who would want red chocolate, anyway?
Construct the structure as if bißchen wouldn't exist. So,
eine rote Schokolade
is what you want. Here we have the basic-level weak declination (eine bißchen Schokolade, ein großer Tisch, ein kleines Pause, and so on).
Bißchen is not a part of this construction, you can use them as if it wouldn't exist.
