It depends which glowlight rasboras you're talking about! There are two species commonly sold as glowlight rasboras;
Trigonostigma hengeli (otherwise known as the lamb-chop rasbora or Hengel's rasbora) and
Trigonopoma pauciperforatum . I'll assume you're talking about the latter, since they look the most similar to glowlight tetras, but please correct me if I'm wrong!
If it's physical differences you're wanting to know about, glowlight rasboras are rather elongate and tend to grow to about 5-6cm, compared to glowlight tetras which only grow to around 4cm but are much deeper bodied.
Glowlight tetras also tend to look a lot 'fatter' and will usually have a silvery sheen on their underbelly, which most glowlight rasboras lack.
They have a few differences in care-- notably the glowlight rasbora prefers cooler temperatures of 70-78F, whereas glowlight tetras prefer 75-82F. Both enjoy a pH below 7.
As for tank size, 15G for both species. You'd want a tank with a long footprint, as opposed to a tall one to give them plenty of room as both are active swimmers!