Howzit & Health New Year!
What is "offered" should not be taken as Absolute but should keep you interested in educating yourself with your physical bodily function and the use of progressive resistance exercise and selected resistance equipment.
The most significant aspect of your workout will be how well you perform the exercises. You will need to have someone with "lifting-experience" to offer what it is he or she sees. Remember that bad technique comes from bad body mechanics. Proper/good techniques comes through clear understanding of what is and what should be. What it is you make "right" can be done Better.
Dumbell exercises are great supplemental exercise that compliments Barbell exercises. DB exercises provides a bit more freedom and reduces stress of joint-muscle action by allowing the shoulder's ball-n-socket to move in a more normal rotational path to where the use of a barbell can hinder and limit the process.
This happens most of the time because the barbell is straight and the exerciser needs to find out positioning of hands-width, the contact spot of the bar touching the right area of the chest, breathing pattern, outward and inward phase-movement of the elbows and correct exercise-posture to stabilize/support the body through the movement. To bring up a few things.
What you can lift with a Barbell Bench Press is different because of the "Centering-stimulis factor" which simply means that there is more involvement of the whole body and you oppose to when using DBs - balancing and structural stability takes a second or two to kick-in.
Good Bench Pressers can Lift say 315 pounds but when they go on to DB Chest Press they can't "cleanly" do in each hand #150.
As for "touching" the DB together, it is best to leave a few inches between them because you will over-do the exercise by making the shoulder-arms do most of the work. The chest muscles stop or hits its peak before the DBs meet.
You can find out where and when if you lie down and place one hand on your pec (either one. you ain't got a big selection) and go through the Press motion and assess for your self than try to keep in mind when actually doing the DB exercise.
Bench Press is a good exercise and Db exercise are good too.
Before closing, please remember that active physical progressive exercises means that you are both student/teacher. The "sense of learning" is knowing that, which you don't know. Always challenge the knowledge that is offered (mine too) so understand what is useful and what is useless and keep on questioning.
Good Health To You and good luck!
mikey