I am favoring Underslung due to the Sprint Speed bonus. This is going to likely be our most common Warp 8 ship during the start of the war so making it as quick as possible will be critical for countering Klingon Warp 8 ships and evening the playing field for our older ships against D6's.
As for costs, I am for now in favor of 1 RF and 2 Regular Launchers for now (depends on what the tactical rating results gets us for each configuration), the cost savings are huge and still gives us a decent level of firepower if we don't roll well on the RF prototyping rolls.
The Impulse Engine numbers were reworked again so it's possible we might not be able to get Very High Maneuverability with the Type 2's which is another reason to keep weapons budget lower but still capable (no way are we going for all Regular launchers).
Here's some damage examples (pulling numbers from
here) including the max 2 Phasers compared to the Canon Connie:
1 RF + 2 Regulars + 2 Phasers:
Alpha: 54+18*4=126
Sustained: 18*3+6*2=66
Torpedo Cost: 15+2.25*2=19.5
Vs 2 RF + 1 Regular:
Alpha: 54*2+18*3=162
Sustained: 18*4+6=78
Torpedo Cost: 15*2+2.25=32.25
Vs 3 RF:
Alpha : 54*3+18*2=198
Sustained: 18*5=90
Torpedo Cost: 45
Canon Connie :
Alpha: 54+24*2=102
Sustained: 18+24*2=76
Torpedo Cost: 15
Canon Connie's Phasers hit harder than ours in exchange for having worse firing arcs, IRC stats where 24 damage and 45 degree arcs compared to our 18 damage and 75 degree arcs.
Overall compared with the canon Connie we can beat it in alpha damage across the board though only barely beat it in sustained with the far more expensive double RF build.
Phasers are 4 cost apiece and realistically we only need 4 at most (16 cost), two in the front and two in the back to ensure that whenever we fire torpedoes it's also being combined with max potential phaser fire.
Note that the sustained numbers are assuming that the ship is able to consistently keep a target in their firing arcs, something that the canon Connie with it's worse firing arcs and lower maneuverability is less likely to be able to do (you can see that when coverage sinks under 100% the sustain number is no longer consistent with max phaser damage for our old designs).
Underslung will probably make this thing quite ugly to look at but war too is an ugly thing so I think it's appropriate.