Whether and how you change the temp as you go is really personal preference. Personally I tend to stay on 6, sometimes finishing a load at 8.is it more effective to begin with the temperature dial low like 4 and then increase by 1 for each hit or is it fine if you go just to 7 and take all hits from there?
and is it normal that if you put the dial at around 7 that after some time the stock stem already gets so hot that you can't keep your lips on it?
To your question on what gets you higher, in my experience using a high temp from the outset seems to get me higher. I think different cannabinoids vaporize at different temps, so if you start at a higher temp you're getting more of them at once. But frankly, I don't think how they all interact is that well understood. But in my own experience, it seems that higher temps get me higher.
It's one of the nice things about the TM: it accommodates people who want low temps, high temps or a little of both.