I checked the official appl site and it says the apple-x 3 is compatible with up to v1.2. My question is - if I flash the applex 3 to a newer x2 bios(4983)on a 1.0-1.2 xbox, will I then be able to use it on a v1.4? Also, how will the soldering points be different?

no it's not possible...
only
- v 1.0
- v1.1
- v 1.2

I have see on a website something to sold an Apple X III on Xbox v 1.3, and I have contact official Apple X resseler and ask...
It's not possible !
Be carrefull with fake of Apple X III, somebody tel "it's possible with few wire add..."
don't believe on this and use the good modchips with your Xbox Version
Apple X Pro => it's compatible, but production is stop !
Apple X 5 => no problem

For the diagrams (in French, but with pic)
Apple X III in JPG
Apple X III in PDF

thanks for the quick reply bro!