Is there a way to know more details about the project without submitting proposal?

When this happens I generally submit a proposal and in the message section just ask the clarifying questions and add that my proposal is subject to change depending on what level of work is required. If you are worried about spending too many connects just to submit a proposal then that's probably an indication that you should pass on the job as I find clients that don't give enough details on what they need aren't the greatest to work with. The proposal is meant to be flexible and not lock you in. That is why there is an additional step of the client needing to offer the job and you needing to accept their offer. This ensures that the details have been worked out between both parties.