Imran, since you have named bread and viennoiserie, that narrows it usefully.
An OTG is fine for cakes and cookies and is the weakest of the three for bread — limited bottom heat, poor thermal recovery when you open the door, and not much mass to hold temperature through a bake. A convection oven gives you even heat and better recovery, and is the most versatile single purchase for a mixed home operation, though the fan can be aggressive on delicate lamination unless you can control it. A deck oven with proper stone and independent top and bottom heat is what bread genuinely wants, and it is a significant step up in cost, footprint and power requirement — it is a small-commercial decision, not a home one, for most people.
Vikram's advice is the right first move. Add mass to what you already have and see how far that takes you, because it costs very little and it isolates whether your problem is the oven or the technique.
If you are heading toward selling bread, the honest sequencing is: prove demand on your current setup with a stone, then buy the convection as your first real upgrade, then move to a deck only when order volume rather than quality is the constraint. Buying a deck oven before demand exists is one of the more expensive mistakes we see.
