I had a quick google and I can see you're right but I think most of these fees (local city, tourist or resort fees) haven't come up for me, as in, I haven't had to pay any additional fee beyond what was shown when I initially looked up a hotel/area. It seems more common if you have to pay at the property that you may have some additional fees added into your price, but I haven't ran into that yet and I've booked with Agoda 5 or 6 times now. I believe part of the reason why Agoda's prices can be more competitive is they essentially have much higher property inventory than other hotel booking sites.

All three hotels are close to each other and located on Soi 6, which is a calm soi contrary to e.g. Soi 4 or even Sukhumvit road. I was only in Citrus Suites. Citrus Suites is a good value, guest and LB friendly, no hassle hotel. The restaurant downstairs is shit (go eating somewhere else). Book a larger room  - one bedroom executive suite - it is worth it. Ask for a room with non-leaking shower. No balcony, so if you smoke, you must go downstairs outside. The pool on the top floor is OK, standard measures for Bangkok. A German friend of mine was in Park Royal and was satisfied. The pool is downstairs and always in the shade. All rooms have a balcony. It underwent a renovation some five years ago. Its name was different before the renovation. Dynasty Grande was  long time closed for renovation. AFAIK, there are no balconies. I have no other infor on this hotel.

Agoda skips taxes and fees to make the price look lower. Be aware of the total.

google

Agoda do have good price , but I find once you find the hotel you like do a google search on it and google will show you a list of price and often the price listing on google is cheaper then search under Agoda for the same hotel Example: GOOGLE - AGODA - $100 Search inside AGODA - $110