I bought an Epever 30A MPPT controller for a four 100W panels. I considered the input amperage but not the input wattage. The max input is 390W. I know the that the panels aren't 100% efficient. Will this work, or am I too close to the limit?
It depends completely on circumstances. A number thrown around is 80% of rated.
Ratings are based on conditions that don't usually happen in the real world, but sometimes a combination of circumstances can even allow GREATER than rated output. My 3kW array briefly put out 3.6kW (+20%) due to extreme cold. Cells were below freezing, and the panels are at 6500' elevation, so the atmosphere is about 15% thinner. Combine those two factors, and I was able to get 3600W in December - 5 days from the worst solar conditions of the year with the panels tilted for "year round" performance. But that's not typical.
Most panels have a NOCT rating, which is a more realistic performance number.