The breakfast buffet pay as you dine costs 180baht when I stayed there early November. The price is really for the place and quantity of the food. I suggest you check on surroundings before choose a prepaid option, there are so many choice within 5 minutes walking if you like Asian food.
Our pool are located on 9th floor in Trinity Complex building 2 minuet by walk cross narrow walk way, and do not have any bar and restaurant there, just refresher drink for sale and sitting area, but they not allow to take any drink to the pool area.
Trinity Silom Hotel (previously Glow Trinity Silom) is just few minutes walk from BTS Chong Nonsi (Silom Line) whereas Nana Plaza is nearby BTS Nana (Sukhumvit Line). You can still purchase your BTS ticket from BTS Chong Nonsi to BTS Nana but you have to inter-change at BTS Siam.