Micro grow.

Ok like it says in the title i have a 1.5 foot tall 2 feet wide cabinate i plan to grow in. I have a few different sativa dominant strains. I was wondering if i should fim or lst or both? And when i should start the 12/12 process i was thinking at about 2-3 weeks of veg depending on growth rate. And mybe start nutes in the last week of vegging.
Any suggestions would be appriciated.

Thanks.