Always try to play around with the ENBoost settings first. They are fickle and system dependent.
Also it is not required to do it for ALL exterior mods... in most cases the usual suspects are
SFO.... do not use that if you do not have a god machine of doom, the extra meshes and varity really gets ya.
SDO... Forceing more stuff to be rendered in full LOD, or full detail, and using ugrids higher then 5... well then you are just asking for it.
SMIM... yes the fancy ropes etc are cool n stuff, but again more complex meshes are by far more taxing then another few 2k textures. Lighting calculations on detailed meshes cost way more then a texture ever will.
"Insert your favorite General landscape 2k texture mod name here" : Examples SRO, SHD, Serious HD etc. All the mods that deliever the majority of exterior textures.
In general a 2Gb card should not have issues with 2k textures in most cases ... assuming that the system is not bogged down with 200 things in the background as well well. Also assuming you do not use any nutty "I want to see what ugrids 11 looks like" settings that force the game to load way way way more... in which case 2GB is no longer enough at all.
So again.. first try to play with the ENBoost settings mentioned. Then try to remove improved meshes or mods that adds loads of new meshes, finally then reduce texture quality.