I've had the same concerns a few months ago.
I did a bit of research on scoobynet and 22b, especially the latter, where the most knowledgable folks are usually on.
Going parallel is good, but not necessary if you're aiming for up to 450bhp.It may be more useful going above that, however Some guys were running 550bhp on standard setup and didn't have issues.
Usually going parallel means automatically using the aftermarket FPR.
Using the adjustable FPR will give u a better control over the fuel pressure and in case u want to max out your existing small injectors. Some kind of getting them flow above their original 100% capacity.
It's really up to you.
I was advised to leave standard fuel lines setup alone,as its good enough for my needs (the 3rd cylinder running lean problem is most likely showing up at higher levels of power) and spending lots of €€€ on braided lines and fittings was not necessary.
I installed Fuelab FPR because I had it already purchased. No regrets. It's running on 3 bar of fuel pressure on idle now so a bit over.. (stock is around 2.8)