I would say to use your best judgment. You can keep em a couple of inches away. If it's too hot for you hand to be near the bulb, then most likely it will affect the plant.. Especially as a seedling. I'm growing 2 plants under a T5 floro system and that is 110 W, but with 5,000 lumens each bulb with a polished reflector. It's great for vegging and would fit in a small area.
Mylar looks like a shiny wrapping paper that can be used to reflect light back toward the plant. Giving you more coverage. Goggle it...
If the area is a bright white, that is just as good.