old, single-glazed windows are unlikely to cause condensation, because they are often draughty, which provides ventilation to exchange the humid internal air with drier outdoor air.
You might see condensation on the glass, because it is cold, but this would otherwise be forming on the walls, which may be worse.
Secondary glazing, well-fitted, provides better noise insulation than sealed dg panes. It will be better if you use a thicker glass than in the original windows. The thermal insulation is not quite as good, but will make a substantial improvement over single glazing.
If you like net curtains, they can make secondary glazing very difficult to see.
If you still have original windows, it is worth having them overhauled, any rot repaired, properly painted, draughtstripped, locks fitted, and any gaps between windowframe and walls repaired. Old putty can be replaced by modern glazing compound and tape, which lasts longer, and does not harden, crack and fall out.