I have been running a vertical grow for 6 years now I think. 2 x 600w in 8 inch cool tubes. A 10 inch filter and an 8 inch fan. Around 1.2 x 1.4m squared footprint cup board. The smaller the space the more need for cool tubes imo. Lots of people work with bare bulbs but I think you need a bit more width to go down that route. Normally. You have oscillating fans pointing up to the bare bud so you have a column of air flowng.over it anyway. Some people call cool tubes, fool tubes but there is definitely a need for them in a small vertical space. I grow with 5 large plants with around a month from clone to decent veg then flip. Yields depend greatly on the time you spend on the grow. Lots of training of plants required.