@blohastik I can at least answer a little on this as I was one who was on the shield version myself a while back. With the change in the system (and adding other mods as well really) expect a minor increase in loading times. I noticed a slight increase in load times with the change over to the vials, but likely because of the increased amount of content in it since the shield version (new weapons, changes in the files a little, more options for spawn rates than just the regular and hardcore that the shields had...) It's just a basic principle, you have more stuff to load the longer it takes to prepare. Also be aware, deleting resources for the packages could also cause issues. I would highly recommend against it as it could cause crashes if the game goes "I'm trying to find this thing, I can't find this thing, I can't continue." Or simply, will just break the content in-game from working properly. Deleting sounds would make some of the guns silent (and who wants a silent gun? I know I don't.) And deleting the mesh changer could actually cause some issues with items in his pack in how they look (if they don't just break entirely from being able to work.) If items are spawning properly without missing parts, work accordingly and aren't crashing your game. Generally I'd say, you got it right.
As for running both at the same time, GJ is going to have to answer on that one more completely. I can only speculate, but I'd imagine though that with running both there may be conflicts between the two that could cause crashing, and the shield already would be lacking in terms of content since it wouldn't have some of the newer items released since the change over to the vial system. Also there could be differences in the items spawned if they could work in tandem if any changes since affected stats of the various items. It'd probably be best just to not use the old version.