Where Should the Sub Panel Go? What Size Wire?
Put the subpanel closest to where the branch circuits exit

I would put the subpanel as close to where the branch circuits exit the house as possible.  This prevents routing and spacing/derating issues with a "bundle" or "trunk" of branch circuit wires from biting you in the butt when you go to hook the branch circuits up to the subpanel.

I'd use 4AWG aluminum for the feeder between the two panels

The folks who say 6AWG is sufficient for 50A are correct, as 6AWG copper wire can handle 55A when limited to a 75&deg;C maximum temperature, which is the general limit for wires connected solely to distribution equipment.  However, at 60A, you are at the threshold where aluminum wires become a cost-effective choice.  As a result, I would use 4AWG aluminum THWN or XHHW-2 in the conduit for the hots and neutral, along with an 8AWG bare copper ground wire.

Your choice of conduit is fine

While 2" conduit may sound like overkill, it's a good choice here as oversizing the conduit both makes the pull easier and provides plenty of space for future expansion.  One could use EMT instead of PVC if they wished to not have a ground wire in the conduit, but that's up to you, really.  One note with PVC, though, is if this garage is not a conditioned space, then you'll need to use expansion joints in the run to keep it from doing the worm on you!

Either way, you will want to provide ample pull points to avoid needing to ask your electrician to swoop in with his truck full of pulling tools and bail you out.  While the inside bends from wall to ceiling will need to be made using prefabricated sweeps, any 90&deg; bends in the ceiling-supported run should be made using LL or LR conduit bodies instead.  

Given your outside wiring scheme, I would go "trunk and branches" here

Given the diagram you gave for your outside wiring scheme, I would run conduit (1" Schedule 80 PVC will do for this) for the main outdoor runs.  In particular, the run from the panel to the first receptacle and from that receptacle to the deck/firepit lights should be done this way, with the pool wiring run as a separate conduit homerun from the panel to provide room for future upgrades to the pool setup.

In the homerun from the panel to the first receptacle box, then, we have:


a 14AWG THWN hot/neutral for the batting cage lights
a 12AWG THWN hot/neutral for the receptacles
a 14AWG THWN multiwire (hot/hot/neutral) branch circuit for the remaining lights
and a 12AWG bare or green THWN ground wire


This conduit gets stubbed up to the first receptacle box, a 2-gang FSS box that has an extra 1/2" nominal (7/8" actual) knockout field-made in its bottom (with a step drill or hole saw) in addition to having 1" hubs molded into the box.  The 1/2" knockout gets used for a 1/2" PVC conduit sleeve (with appropriate fitting) that protects a 14/2 UF cable going down into the ground for the batting cage lights, while the other 1" hub is used for the conduit onward to the deck/fire pit lights.  In this conduit, we have the 12AWG for the receptacle branch circuit, the 14AWG multiwire branch circuit for the deck and fire pit lights, and a 12AWG ground wire.

When we reach the deck/fire pit light switch location, we stub up into a 2 gang FSCC box with 1" factory hubs.  This box houses the light switches, or if you prefer, just splices with the light switches in a 2 gang FSC box mounted further up on the structure.  From the light switch box, we then head up to the light fixtures in more conduit; if you need to, you can split neutral in half at the switch box and have two neutrals in the conduit from the switch box to the lights, even.

The other stub-down, then, can either be a 1/2" conduit to the ground with a reducer at the box if you are running a 12/2 UF to the other receptacle location, or 12AWG THHN in conduit (either 1/2" or 1", your pick) for the entire run to the other receptacle if you prefer.

TORQUE ALL LUGS TO SPEC

One other note is that when you are installing panels these days, 2017 NEC 110.14(D) requires that you use a torque tool (torque wrench or screwdriver, reading in inch-pounds in practice) to tighten all lugs on devices labeled with torque specifications to that labeled torque.  Even if your jurisdiction has not adopted the 2017 NEC yet, it's a good idea to do this anyway, lest your electrical system loses you the race.