Circular Needles help

Soooo today I bought a pair of circular needles after the lady at my local yarn shop recommended them. They’re ChiaoGoo 24”. I started my “project” (just practicing as i’m very new to this) over on them and I liked them, but when I went to knit my first row and got to the stitches (?) that were at the beginning that went onto the cable, it was really hard to get the needle through and I just decided to frog it and will try again 🤷🏻

my questions are: - Can you really use them the same as straight needles like I was told today? - Is casting on any different? - Why were the stitches or loops so tight even though I casted on the same for all of it?

I’m not sure if it’s the needles or my cast on.. I like the feel of them, but I’m confused with if the cable being thinner messes up the tension/ cast on? Occasionally, I cast on too tight and will restart with straight needles, but mostly have been getting pretty good tension IMO, so I’m trying to figure out what’s different this time

Also, my cast on is with a slip stitch and then I’m looping yarn around my thumb and catching the loop on the needle, I’m not sure what cast on it is called (thumb cast on?) but was taught in a knitting tutorial. Should I be using a different one? What’s a solid, universal cast on that gives consistent tension?

TIA!