I’ve mixed songs using FX starting from scratch, only to find out that there was a preset that had nearly the same or exactly the same settings. In my opinion, you just have to know what sort of result you seek, check to see if there’s a preset for it or not, and work from there. If there’s a professionally developed preset, there’s chance it will work with nothing but minor adjustments if any.
In the end, it is always going to be better to understand what the plug-in does and how to work with it from its initialized state even if you do nothing but use presets 90% of the time for efficiency. If you don’t understand the plug-in, “tweaking” means “experimenting and fooling around with it” instead of “fine tuning”. You end up wasting time or possibly making it sound worse rather than better.