I've been reading all the posts and information I've found... But after all this time looking this mod...i have...questions
You are simply looking at the wrong place... right place being the devellopment forum who can only be access by mod dev and mod leaders...
First question: In the final mod, have we only two cap. ships, the supercarrier of the UNSC, and the Assault Carrier of the Covenant?
Final mod is not for soon... and it remain a lot of model to make... phoenix class and covenant supercarrier ( not the scaled 5 time assault carrier from Halo reach but the real covenant supercarrier ) will be the next...
For the phoenix, he is in texturing stage now... take a long time become a lot of 3D detail are added via Xach-effect, a lot more effective that with bump map or nm map in sins...

One "wings" is only 4 triangle... basic plating use bump map and the details with high relief ( 3d effect ) use a Xach-effect
Second question: Have the UNSC ships only two type of weapons? (MAC and Archer missiles)
Nope... take a look at a old screenshot for the phoenix just below...

You can see ATAF missile turret and deck gun... since i have made the UNSC supercarrier, these have the shiva nuclear missile... having work on the frigate too, these have the 50mm flak gun too...
Pretty sure that when our list of model will expand, we will have the Morey space mine... normally, UNSC carrier have two
fusion rocket... slow and non effective against covenant ship but work good against orbital structure... there is the more big UNSC weapons, called Nova bomb... don't think that it is already implemented on any ship from the mod but it is a very interesting bomb :
"The only documented triggering of a NOVA Bomb...The resulting explosion occurred between a Covenant outpost planet Joyous Exultation and its moon, Malhiem, scorching half of the planet and shattering the moon. The resulting winds on Joyous Exultation flattened cities and spawned tidal waves. Radiation flooded the planet and killed everything living on it, penetrating the surface of the planet to its core. Every ship within the NOVA Bomb's range, save for those on the opposite side of the planet, boiled and vaporized in an instant. It is unknown what the Covenant did with the planet, but it is no longer capable of supporting life. The NOVA Bomb explosion completely destroyed three-fifths of the fleet that was there, totaling over 300 ships."
In fact, UNSC ship can have plenty of various weapons, several of them not being good documented and having mainly reference only in the Halo novel...