I'm generally a Vanilla player which is my most of my modding work is focused on stand alone modules.
The three main D:OS mods for the main campaign:
Scales - The main benefit of scales is most(all?) of the changes don't require a new saved game so if you were already playing a game you could install it and try it. But you probably can't remove it cleanly after it's been installed. So if you wanted to try it out you could say get up to level 3 and make 2 saves, one clean and one with scales. See how it goes and if you cahnge your mind, uninstall (probably backup the entire game directory since Scales is not a mod proper but actually modifies the main campaign files) you could go back to your old save and keep going vanilla. Scales is explicitly intended to add more challenge on tactician mode where as I don't think the other two are.
XC_Bags - I'm not as familiar with this mod, FrauBlake is around and I'm sure he can chime in. Generally it's a mod that has automated inventory handling and a lot of crafting changes. Some other stuff too like some old skills are added back, a few new ones. bug fixes. The rather massive changelist is in the thread here.
The other one you didn't mention is Better Logistics
http://www.nexusmods.com/divinityoriginalsin/mods/92Which has a lighter touch than both of the other two but features similar inventory management helpers to XC and crafting changes without some of the extra non-vanilla stuff. But it's also compatible with Scales so you could pick your flavor that way.
That probably wasn't much help :P. Just gonna have to figure out which features you want. Personally the inventory management features, while impressive script wise never did much for me in-game because I simply just ignore inventory management. There's not much reason to mind it anyway since your weight limit is insane. I also don't like crafting much. If you care about crafting a lot using a mod probably makes sense.
