As per usual, this mod has two versions:

The Doom graphics version is suitable for all ports that support MBF21's DSDHacked featureset.

The paletted PNG graphics version is suitable for Woof, Nugget Doom and GZDoom. You should use this version if you wish to play Twice a Veteran with WADs that feature their own custom palettes, as the graphics will be converted into said palette a little nicer.

As of v1.2, the mod also comes with an optional sound patch (Medal of Honor sounds) made by Dr_Cosmobyte, which features slightly more accurate sounds to the original game.

Some tips:
You switch to and from the pistol and Duplet shotgun faster, as they're one-handed weapons.
The flak cannon does have self-damage, but don't be afraid to get close to it - its self-damage range is pretty short and unlikely to kill you.
The Garand reloads every 8 rounds, but is a fantastic sniper-type weapon and will one-hit kill chaigunners and below. Don't get caught mid-reload.
The Duplet has more spread than usual, but it spits out 25 pellets. It's a superer shotgun!
The riotgun, on the other hand, is a good deal faster than the vanilla shotgun with a little worse spread.
The flamethrower shoots in 5 "round" bursts. Tap-fire it if you want to try saving some ammo.
The bazooka offers insane damage, but it can also kill you if under 200 armor/health. Since the rocket spawns with an offset, DON'T HUG WALLS TO YOUR RIGHT or you will BLOW UP.
The humble Tommy gun can also be tap-fired for more accuracy.