So I started my 40 BR in March and have taken a liking to the whole thing so I am starting to make the set up nicer and invest a bit more money. I have about 50-60 lbs of rock, just grabbed a Eshopps PSK-75 skimmer to hang on my sump and and in the process of adding a fuge in the sump, dual chamber reactor I made filled with carbon and phosguard. Also just grabbed a 4x39w t5 to start out with some zoas, shrooms, softies and lps.

I currently have:
Pair Black ORA clowns'
Royal Gramma
6 Line Wrasse
Purple firefish
2 Peps
and a beat up CUC since my blue hermit loves to eat snails.
I'm going to be adding about 10-15 more assorted snails to get more of a CUC in there

My question is in regards to adding more fish. Is this thing maxed out? My params are all perfect and have been consistently great since the tank cycled. I will admit though I slack on water changes and do 5 gallons every 2-3 weeks.

I was thinking of adding some (3) Green Chromis because I think they would add some life to the tank and school up. The firefish and gramma are nice looking but otherwise pretty boring. Any input is appreciated.

You could have more fish, but a chromis trio are a bad idea because they don't do well in small groups. A small dwarf angel species (genus Centropyge) is one option.

I agree on the Centropyge or you could do a single smaller anthias, try to stay under 5" as an adult male if you can. A sunburst/fathead anthias may be a good choice.