The pros all use heavy internal shoulder rotation
(ISR) to provide final racket head speed to their serves. To do this you must 'load' or stretch the ISR muscles. One main component of the stretch is the leg thrust. You can leave leg thrust out or reduce it so that your feet don't leave the ground.
There was a thread discussing serving without leg thrust.
You can also stretch the ISR muscles with complex trunk motions (lumbar lateral flexion, lumbar rotation
) and other mysterious motions in the middle of the service motion.
The ISR service motion is being used by all pro tennis players. When done properly by a conditioned athlete the technique seems to be very safe especially considering the violence of the motion.
Most recreation players - lower performance - have developed their own serving techniques probably using what feels good as a guide. For recreational serves, I believe that many/most players use ISR and have no idea. Only a high speed video can determine what they are actually doing. I took high speed video of some of my tennis friends and saw ISR, often much more than in my serve. Very often these players keep their shoulders too level - an injury risk specifically identified in the Todd Ellenbecker & Jim McLennan videos. This 'too level' shoulder orientation adds to shoulder impingement injury risk.
There is a risk of developing your own technique since there no track record regarding injury issues compared to the pro serving technique using stretching followed by very rapid ISR.
Only high speed video can show you what you are doing on your serves. Video 60p with fast shutter and small Jello Effect is also useful but the fastest part of the serve needs high speed video to observe.