I can't speak to the Continental Style of knitting, however I do believe fast Continental knitters knit faster than fast English knitters.
That said, I'm an English knitter (throw the yarn)...and I get more knitting done than anybody I know. Sometimes it's not how lightening fast your needles blaze, it's how effective you are at knitting the pattern. Preparation can mean less mistakes, and less frogging and tinking. Keeping/making good notes also makes the knitting part go faster cuz you always know what to do and when to do it.
To be FAST isn't the reason to learn Continental knitting. There are assorted reasons it is a great way to knit. Less tedonitis I've heard. You are better at Fair Isle knitting cuz you can knit with both hands. In about a minute, lots of Conti knitters are going to add their 2 cents. I'll say this: if you are ever going to learn Conti knitting, it's better to do it as soon as possible. The sooner you force yourself to learn it, the easier it will be to switch! It's too late for me!
About casting on too tight: it can cause your knitting to be too tight as well.
A tight cast on just starts the whole thing on the wrong foot.
Here's what to do: If you think you will be using (for example) and US8 for your scarf...cast on with a US9. Then on the first row of knitting, use the US8 in your right hand...and from then on, use the US8 in both hands.
You could even try going up 2 sizes for the cast on needle. Just keep tinkering around with it until you like the results.
Make a practice swatch for casting on and knitting a few rows before you cast on a huge number of stitches for the real deal.