l know it can vary depending on the specific journal and field of study. However, generally speaking, and in your opinion, what is the best time to submit a paper?
From my experience, the time spent under review was slightly less for manuscripts that I've submitted in the winter, and/or in early spring (Dec - Apr). However, it really depends. There could be special issues/conference proceedings that can determine a significantly higher number of submissions than average within certain journals and therefore this could impact the speed of decisions.
I think it makes the most sense to submit a paper when it is ready, rather than wait until later. The sooner the paper is published, the sooner it will be available for grant reviewers, and this makes reviewers more likely to fund you. I know of a lab that published no papers for a while because the PI was in the hospital long-term. The grant was not funded. When the PI returned, the lab published 8 papers from the data generated while the PI was away. The grant was funded in the next cycle.