The house you like and saw 3 times, all by the same agent? If so, that agent should submit the offer. And, you should insist the agent present the offer in person. When done, the seller should sign something that says the offer was received.
Do not try to use a variety of agents, keeping it a the secret from them. Use one agent, always your choice. Agents who are well trained and have experience in business and/or are intelligent will out perform old timers every time. Real estate is a profession of "keep doing whatever works". Many ask themselves, "what can I do different from before and be better." That is who you want to represent you.
On the offer, it is mostly about the money. But If you have a great credit score, reveal that to the seller thru your agent. The closing date might be the key to acceptance, if so emphasize it thru your agent. But stick with the agent who works and found the house and showed to you 3 times, if that is true.