Soluble and insoluble fibre is a useful start, but it does not explain everything.
A better question is: what does the fibre do? Viscous fibre thickens when it meets water. Psyllium husk is the classic example because it forms a gel. This can support fullness and slower meal movement, but it also means the product must be taken with enough water.
Fermentable fibre is different. It reaches the large intestine and becomes food for gut bacteria. Some fermentable fibres may support short chain fatty acid production, which is why they are discussed in microbiome nutrition.
Prebiotic fibre is a more specific idea. It is a fibre or carbohydrate that is used by beneficial gut bacteria in a way that may support gut health. PHGG, acacia fibre, inulin and resistant starch are often discussed in this space, though tolerance can vary.
For Indian meals, this means no single food solves everything. Dal, vegetables, fruits, oats, millets, seeds and fibre supplements all behave differently.
Choose fibre by purpose. For regularity, water holding may matter. For microbiome support, gentle prebiotic fibre may matter. For daily eating, variety matters most.
There is no single best fibre on this list, only the one matched to the job: a gel forming fibre for fullness, a fermentable one for the microbiome, or plain variety for all of it at once.