http://www.tesnexus.com/downloads/file.php?id=19510

my PC is pretty low end.

the mod mentions some tweaks to the graphics.. is it more demanding graphics-wise than vanilla?

I don't think it makes things any more demanding, no. The main intent for those, I believe, is to give modders a few new options moving forward.

I highly recommend you get MCP, as all the different patches it has are modular and thus you can choose what you wish to apply. There is a thread dedicated to it that you can peek through for more info as well, but all in all, get it and use it (there are some patches in there that are simply must have, as you will see when choosing your patches - they all have descriptions).

It fixes a few graphics bugs but it doesn't add any real graphics improvements, so no there shouldn't be a performance hit.

The Morrowind.ini tweaks recommended for the 'Rain/snow collision' patch might impact performance during rainy/snowy weather on older hardware, but you could always dial down the number adjustments in the ini.

Actually, the top 2 graphics improvements can be intense. Others not at all. You can still test it for yourself, when it is Morrowind, it is hard to make generalizations.