Batch editing hundreds of .stls - need help! :)

Hello! I have few cases in which I need to work on hundredts of .stl files and make a simple modifications to them. I am trying to look for a few days for some batch editing ideas but I am running in circles right now. I don't even know which software to use, best would be possible to work with comand line to automate it. I have already tried Prusa Slicer Console and Slic3r console, but they do not have the required options. Case 1 - I need to batch simplify models. I have pretty simple models (for human perception) that have way too much triangles - over 1 milion, they can weight over 300 MB and simplifiyng them in Prusa Slicer manually by only a small steps already gives me models that are 30x lighter and don't loose any details. How could I do it massively with automation? Case 2 - I have hundreds of models that I need to make simple changes on them - increase Z, Cut in given Z, store only the lower part, resize. All of those tasks are 100% the same and repeatable. How could I do it massively with automation? Would love to get any ideas guys and girls :) The solution does not need to be free, but it has to do the required task :) Thanks!