No matter how bad your transit is, it will without doubt be a much more pleasant experience than transiting at LHR, LGW.
Usually the staff are pretty much ok, and yes, you may have to go through security again. As for a direct route, I cannot help. As pointed out above, the security checks are usually right at the boarding gate, so in order to take any water/juice aboard, you need to buy it in specific shops (just ask), where it will be expensive, and they will wrap your water bottle in a sealed plastic bag. It is important you do not open it, until you are on the aircraft.
Before the new liquid regs, this problem didn't exist, but at least there is a way around it.
As big airports go, Schiphol is better than most, just remember that if this the first time you have transited like this, keep checking the signs/boarding gate, check all the time. Never assume anything.
I can recall many years ago, running at break neck speed to catch a connection at LHR to Stockholm. I made it to the gate just in time to be told, it was the wrong airline, and I needed the BA stockholm flight, departing five minutes later, at a far away gate. You look at the board, you see stockholm (I didn't check the airline name), you run. Easily done.