Yeah, there will be light map leaking between the UVs that are so close together.
When you generate lightmap UVs in the engine (which is totally a reasonable thing to do!) you get to set “light map minimum resolution” which determines the padding between the charts. The HIGHER the “min resolution,” the LESS padding there is in UV space – this makes sense if you think about it; when the light map is bigger, the same number of padding pixels will take up less UV space. I usually crank it up to 256 or so.
It’s usually also always better to make UV charts as well connected as possible, while still nicely packing the available texture space. Generating one chart with four rectangles for a strut in the shelf, is going to be better than generating four separate charts, one for each side of the strut. In 3ds Max, this would be the “cylindrical” mapping preferred over the “box” mapping; I’m sure whatever tool you use has similar choices.