Can I just get a clarification on what is allowed for measuring when?

I believe the rules say that you cannot use the maneuvers and plop them down to see how your move would turn out during Planning Phase, but its okay to hold them and eyeball it.

Can you "measure range" during Planning Phase? The range ruler R2 is equal to 5 movement.

During Activation Phase, can I place down maneuver templates on other ships to better judge whether I should do something like a barrel roll?

Say: I Intel Agent'ed a ship in front of me. And now I'm trying to decide if I should barrel roll.

According to the rules, you really only can measure range when you are doing something that requires it. In other words, if you need to get range for an attack, you measure then. In Tournament rules, you can't even measure until you declare a target. Same with Target Lock, you select a target, then measure to see if it's in range. If it is you MUST target lock that ship.

So you can't measure when you are planning your dials because nothing requires you to measure.

Thanks for your awesome clarification. It makes a lot more sense now!

I'm assuming you are fairly new to this game, so please don't take this the wrong way, but I would suggest you re-read the rulebook and the latest FAQ. A couple of your questions have clear answers in the rules and the FAQ.

When I first got my core set, I couldn't wait to get stuck in and have a game, so I just skimmed over the rules and started muddling through a couple of games. BIG mistake.

Read the rule book often, as you'll find something in there each time. I've actually found it useful to download the pdf from the support page, as you can search through it faster with CTL + F to find a particular item.

Fly casual.

I was just told during combat you can measurerange from your attacking ship to multiple ships to see which is in range 1-3

Yes, that is in the FAQ.

When a ship becomes the active ship during the combat phase, the active
player can measure range from the active ship to any enemy ships before
declaring one as its target.