I would leave it alone myself. Especially the chrome bits. I don't know your model of bike, but Peugeot usually spot welded the "braze ons" on.
I'm not a big fan of cleaning up lugs after the fact. Who knows what you might reveal? There are bound to be voids under those lugs; to completely fill them would have taken longer than it was worth for Peugeot. A pressed steel lug almost always has gaps where the metal was bent and welded. The welds were crappy enough that it would be very difficult to fill them without adding another step to the process. One look at these bikes will tell you they didn't take any unnecessary steps.
If you clean up any stray filler, make sure not to cut into the tubes.
Originally Posted by
Scooper
It's not a good idea to file the edges of the lug so much that the lug "feathers" into the tube as that removes too much meat from the lug and could compromise strength.
I can't see why this would be correct. Most builders don't do this because it's not what people want nowadays, but the UK builders from back in the day would feather their lugs, and there were plenty of U.S. builders that did it as well. I imagine feathering was mostly done after the fact because otherwise the lug would be hard to braze.