cr.Mk Hadouken FADC range consistency?

Getting back into SF after a long break I noticed a few things during training that sometimes at the same distance the FADC doesn’t always connect if I am not holding forward before I chain my next combo(cl.HP or w/e). Is it some sort of kara integration where holding the forward from your FADC that gives you the extra range?

On a related note do you guys really notice a difference or is there a difference of which Hadouken you use? I see some people mention that the lp Hadouken gives more confirmation but I am more re-actively confirming off of the cr.Mk.

Would enjoy any elaborations on this thanks.