The taxes/charges levied on tickets are, for the largest part, published independant of the aircraft size used on a flight. No refunds if the plane is smaller or cheaper (which doesn't necessarily have to be 'smaller', but could also be 'quieter'), just as there aren't any extra invoices to pay if your flight is operated by something larger/more expensive than originally planned.
The taxes/levies/charges that are dependant on things like weight are usually calculated into the fare by the airline, and will usually be calculated at a type of average accross the types of aircraft used on a flight.
If you can find a route operated by several different types of planes, take a look at the taxes/fees charged on the different types: usually, you'll find out that the taxes are identical, regardless if the flight is operated by a B737, an A320, a B777, an A330 or whatever else.
As for the side-thread about what has to be advertized - here in Germany you have to list the price that's printed at the bottom of the ticket in the add, i.e. fare plus taxes/charges levied on the ticket itself (which is why LH
will constantly advertize €99 fares throughout Europe, though you've got 0 chance of actually buying it at that price: ticketing/service charges charged by the website/travel agency/airline go on top of that, but those, too, have to be mentioned in the add).