Systemic are more designed to be used away from food and be absorbed into the system where they act upon stray proteins and fats, etc that can be blocking the circulatory/lymph system in all tissue that these feed. What it will do (as long as your lifestyle is now healthy) is work to rejuvinate the flow in your system. This has incredible impact. It allows good nutrition to flow freely as well as metabloic waste to be transported easily to the elimination organs. It reduces inflammation and all kinds of problems due to autointoxication. It is not a bandaid, in other words it works together with proper nutrition to rebalnce the system.
Imagine if the roadways in a city were blockaed here and there, how would that affect things?
As far as digestive enzymes, they are taken with food in order to efficiently break down food into useable form. This function is often ailing as we abuse our sytems with poor lifestyle choices. This "crustch" helps us until we have detoxed, unclogged our flow and rebalanced our nutritional status. Then we no longer need this assistance as a proper uncooked (natural) diet will keep us in a balanced state. If we return to eating mucous forming, acid creating foods(meat, grains, dairy), then we can start all over.
There are vegan options for both systemic and digestive ensymes.
Systemic: vitalzym and FYI Restore (Garden of Life)