A preventative outcome for what exactly? You have a plethora of different trees, each with their own potential issues. Copper is great for fireblight, a mediocre and low efficacy fungicide. Neem oil is great for mite or aphid outbreaks, but again very low efficacy, almost a waste as a preventative. 

For your stone fruits, brown rot is potentially one of your most prevalent, worst diseases. And maybe the plum curculio, your most serious insect. 

For your apples, apple scab is the most prevalent, serious disease. And likely coddling moth your insect to prevent. 

Fungicides always need to be preventative, and insects you can treat for as a part of an IPM plan. A great preventative fungicide I recommend is myclobutanil, which could spray half as much as an organic copper, and achieve a better result yet. 

For insect outbreaks you could try permethrin, or an organicaly derived pyrtheroid, if you wanna stay organic. Neem oil can also be used, but you may find it does not work against some insects. 

Here is some reading from the EPA on the topic of IPM:  https://www.epa.gov/safepestcontrol/integrated-pest-management-ipm-principles

*Always apply pesticides according to labeled instructions, observing labeled pre-harvest intervals (PHI).  

Best of luck.