So yeah downloaded the hi res texture pack and I have trouble with the game crashing whenever I go to load an exterior cell, indoors the game doesnt crash but whenever I go outside it just exits to desktop, anyone know any solutions to this?

Also while the texture pack works indoors I really dont notice that great a leap in the quality of the textures, is it only a subtle difference or is there something wrong with my game? I also plan to use mods so I was also wondering if any mods require me to have the texture pack or if I can do without and download a better user created texture pack?

No mods require the texture pack so you can turn it off. Main culprit for issues with it are 32 bit OS so if you have one of those I would leave it off. Other than that you could be running into your VRAM limit on your graphics card. To disable it open your data files in the launcher (under options) and unclick both boxes.