should a mod like this be used to improve performance? yes

should this mod be used to make the game look better? no never always use another mod like pfuscher 2020 or somethign similar if you want the game to look better

what do i recommend for textures? noble skyrim or skyland

does this replace other performance mods? no, this should be used with other performance mods always like sse engine tweaks or display fixes

can i use ultra settings? only if your computer can handle it, remember when using mods to be realistic in your expectations. gaining performance comes at a cost whether it be through reduced visual quality  or through a loss of certain features

can i do the textures of this mod or that mod? not without the authors permission, most will prefer to do the job themselves or will simply not wish to do so for various different reasons

can i convert the textures myself? yes you can, but do you have the time or a computer with high enough specs to do so, do you know which settings to use so that you do not accidentally mess something up. just because you can do so does not mean that doing so is a good idea

i didn't see any improvement in performance? the increase in performance is not always obvious, and there will be some that never see the improvement because of the mod setup that they use & the settings that they use (i myself have a hard time spotting these improvements because i use a lot of texture & mesh mods, but i know it is there because i did testing to verify that the results were as i expected them to be using various mod setups with different settings).