Time and memory are often two different things :) Although if memory runs out, it will affect time, since things will start paging etc.
So, saving memory - less render elements is better, especially elements like LightSelects. Denoising outside of the 3D app can help. Or, not Denoising at all and simply rendering for more passes may be more effective, and could even reduce render times if it means you no longer run into low memory situations.
For time, personally I find that as resolution goes up, the Noise Level you render to can go up as well. That is, you can render for less passes in a higher resolution and get a result that is as visually pleasing (I haven't put that to a scientific test mind you). So, higher noise level and / or less passes (depending on which you are using) could help.
Then there is indeed the option to render in strips or image sections, and then combine them back together afterward, if it becomes really necessary to save memory (e.g. you absolutely can't remove any more render elements, or absolutely must have Denoising on all passes, etc.)