I always end up with 100 in sword skills too fast compared to other skills and the playthrough. Is there mod that would slow these? I've used niapets leveling mod, but they also slow magic skills which I feel then level too slow for the playthrough.

There's http://www.moddb.com/games/morrowind/addons/ism. It makes it so higher cost spells will improve your rate faster so you don't need to grind lower magicka spells. I think the feature might be included with some other mods.

Thanks, I wonder if that works with niapets leveling mod, so I could have slower overall skill gain and then magic skills leveling faster in relation?

Yeah it should be. It doesn't change the regular overall skill gain and it was made to work with GCD another leveling mod.

Edit: Actually it's made to go with GCD. It says without GCD it's a bonus that won't affect your leveling. I forgot about that.

Thanks I'll try ISM with GCD.

There's also the ellis community uncapper, but I don't know if it works with your mod. It lets you set up all the numbers, from how potent skills are, to how much experience you get for the skill, and how much the skill gives towards a level. You can even set it between specific levels, so for example, you can set it to get experience for one handed normally up to level 50, then set it so that you get half of the experience between level 50 and 75, and then take it down to 0.25 of default experience from 75 to 100. If your mod is strictly dealing with a plugin file you should be fine, because ellis uncapper is just a notepad-like file that you edit.

The one suggested by nightmirror is probably better if it was made to work with your mod, I'm just giving an alternative option.