If you use a 94% efficient driver like Meanwell's HLG-Series you get 6w of heat every 100w's.
A HLG-320H should produce ~20w of heat @ 220/240v.
If you use 110/115V effiency is a bit lower, ~91%, so 9w heat each 100w's.
This means a same driver would produce ~30w of heat.
This is not as much but it is noticeable, especially if you are living in a hot zone.
If you need the heat to reach 27-30°C canopy temps in your wardrobe put it on the backside of the frame.
I imagine an ozzilating fan hanging in the upper corner blowing downwards, it helps a lot to increase the temps at the bottom of the tent.
But if you really consider to use more as 35w/sft. I don't think you'll get problems reaching this temps.