Measuring sails

I have "new" to me Shore sails in very good condition. Is there a way to measure the jib to know what kind of rig it is?
Would having the forestay or shrouds too tight affect my pointing?

There's a lot of information at this link:

Yep. A lot of info and none of it useful.

The best way to verify what you have is to measure across the seam directly below the top batten- luff to leech. If it is very close to 38" it is a snug jib if it is closer to 40" it is tight and if it is more like 35" it is a loose rig.
Forestay tension, jib halyard tension, and mast rake all have an effect on pointing.