As you can tell by the answers, so far, you are dealing with the exact issues as everyone else, when they first start carrying.
As far as position, it will depend on several factors, ease of deployment, comfort, clothing choice, whether you spend more time seated, or standing, etc. Practice your draw, from each position, and see which one feels the most natural, requires the least amount extra motions, and allows the quickest target aquisition. Practice wearing different clothes, such as lightweight summer clothes, to heavier winter coats and jackets. You may decide to change positions with the change of seasons.
As others have said, there is no perfect for everyone, holster, or carry method, it will be a matter of trial and error, most members here, have several holsters, stuck in a drawer that after trying for a while, didn't do the job.
Becoming comfortable with a loaded chamber, will come with practice, with an unloaded gun, reholstering, transitioning, and trigger discipline. In my opinion, worrying too much about reholstering, without looking, is not a major concern. No one has ever won a gun fight by being the first one with their gun back in their holster.
Good luck, and obtain as much training as possible, glad to see more young people taking their own security seriously.