Even if you branch off your main bus with more 14 AWG, one joint
isn't going to hurt you. My main bus passes through several screw
terminals before the power arrives to the track. Bottom line, if
you can pass the quarter short-circuit test, you are good to go.
I wouldn't think whether you used a DC or an AC source would
matter. If a device can operate on AC, then if you use a DC supply,
it will still pass through the same circuitry inside the booster as
if you used AC - generating the same amount of heat. We will have
to see if anyone else knows any differently. What I think is
important is that your source, whether AC or DC, not put a voltage
that is significantly higher than the anticipated track voltage.
The differential will certainly be dissapated as wasted heat in the
booster. If you use the PS2012 for example, don't set it to G-scale
and then run your boosters set to HO.
I think you are fine with your plan on Loconet jacks. Even if you
have friends come over, I think most people have gone wireless.
Everyone I know in my area has done so. Besides, if you have enough
throttles to provide to your operators, you don't have to worry
about people coming over with a non-wireless throttle.
Having the jacks near the yards and such is good for two reasons.
1. So you can assign engines. 2. There appears to be a slight
delay when using wireless. So some of us do our switching plugged
in to a jack.