what's better for dhc phaser's ...pre fire chamber or phaser relay? does it really matter?

Prefire chamber is only for cannons, phaser relay is for any phaser weapon. So if you have all phaser cannons it doesnt matter. But if you have a mix, say two DHC and a beam array, then you want to go with phaser relay. The mods are the same- up to +26 it just depends on your weapons mix.

its all different now on tribble. just get the energy type consoles, prefire and beam consoles now suck and give half the bonus they used too. very bad investment going forward

Not quite half, but, yeah. Blue mk XI cannon and beam consoles are +18% damage, torpedo console is 16%. Type specific mk XI blue consoles for both kinetic and energy weapons are 26%.

The interesting thing, the cannon and beam consoles now say "all energy damage," so they both seem to apply to both beams and cannons (haven't actually tested this, but I think I might later). The new system seems to ignore the distinction between different weapon types so beam/cannon mixes might be more attractive, but still segregated energy types so rainbow ships won't be catching on any time soon.

AFAIK you are correct. Part of the skill revamp was to generalize weapons and ship types so we'd be able to play around with weapon types or ship classes.