1.) That looks to be SFC OP. Could be SFC2. Can't really tell, but I'm betting it's OP. What mod it is and where it is, I have no idea. More than likely the ships were just added to the install manually by the person who made the vid. Those Connies however look like WZ's Connies.
2.) The only thing OP doesn't have are the storyline missions from EAW. Other than that, OP has everything EAW has and more. This includes races and weapons.
3.) Depends on who you ask. There's currently a hardcore testing server out right now for OP which is fairly good. Same old shiplist that's been used for years, but the missions help spice things up a bit. There are some good mods for SFC3, however not much is going on these days when it comes to the D3. The GFL have released Legions At War 5, a Dynaverse 3 campaign. Check it out.
If you're asking for ships though, there is an abundance of ships for SFC, all versions. All versions use the same format. SFC1 doesn't use lightmaps, and SFC2/OP and SFC3 have different hardpointing systems, but those are minor issues and ships can be ported to any version of SFC.
4.) Legacy, graphics wise, is a great game. Other than that, it still doesn't have much else. The major mods, such UU and TLG, do help the game quite a bit, and there are scripters for Legacy that continuously work to improve the game. However, only one official patch was ever really released, and then support for the game from the developers pretty much ceased.