> Ive seen players open 2x with 7cards, 10points and 3x with 5cards 7points,
> completely opposite to what I was taught way back when I joined BBO. Since
> then I have learned vulnerability and position are a major consideration but I
> don’t understand why you would flip the openings like this.
Preempting is a lot more complicated than following rules. Seat/vulnerability/jugdement issues play a big role. When you learn preempts, you're tought only the basic requirements. Experienced players go a bit further because they learned (sometimes from painful experience) when to twist the rules to open 2x on 7 cards, or 3x on 5 cards.
I'd like to give you a reference on advanced preempting, but, unfortunately, good books on advanced preempting are very rare. I only know one: chapter 3 of Robson/Segal. I think a .pdf of it is avaliable somewhere in the internet. You can try and google it.
> I have a probably bad habit of downgrading poor 3x preempts to 2x when suit
> and vulnerability are against us.
That's not a bad habit. That's a good habit

If the hand is too offensive to pass and the suit is bad, 2x is a good compromise solution.
> When would you change a 3x preempt to a 2x or visa versa
Definitely downgrade when the suit is bad and vuln is against you, e.g.
KJxxxxx
x
QJx
xx
seems like a 2
♠ to me. As for upgrade, do it at NV and with a good suit and an otherwise worthless hand on defense, e.g.
x
QJT9xx
xx
xxxx
seems like a good 3
♥ to me at NV, 1st or 3rd seat. Not in 2nd seat because chances are pard has as much hcp as LHO. If he takes you too seriously, he might be disappointed. Still, a 2
♥ sure is ok, even despite the low hcp count.