I would tend to think that at 16 you may be reaching you height potential - but that is not a definite. You usually don't stop the growth for height until you are about 18. If you remain a player of smaller stature, I would concentrate of developing your abilities as a winger or outside midfielder (right or left half) on the reasoning that, if you are of smaller build, it is no use trying to compete with centrebacks who are usually chosen for the height as much as their football skills. If your shots tend to be 'lobs' being in a wing position means you can turn them into' crosses' - or 'assists', as it seems to be termed in the USA. As for upper body strength, that will start to come as you get older. In normal situations, we don't actually reach our full shoulder width until we are well into our twenties. Some gym work may, of course, help.
If you are already a fairly skilful player, your next best asset to develop is speed. If you are playing full games, you will naturally build up stamina to keep running for a full game - that is fine. But what usually makes the top strikers stand out (ie. Fernando Torres, Stephen Gerrard, Wayne Rooney) Is extreme speed over a short distance. ie. If you concentrate on being able to cover a 10 metre sprint faster than most defenders, it will give you the speed to get around most of them. Remember, the beating of the player is actually in the first 5 metres!
Ask yourself... how many times do I have to sprint the full length of a pitch at top speed all the way? answer... not very often, if ever! Then ask... how many times do I have to sprint a very short distance to go for a ball pushed past a defender? answer.... all the time!
If you develop extreme speed over short distances, it gets you clear of defenders and gives you room to get in a cross.
As a practice drill to develop speed, do sprints from the goal line to the edge of the penalty box (approx 15 metres) and time yourself! Aim to cover the first 10 metres as quickly as possible. Keep trying to lower your time. Then do 'one on one' sprints with other players in your team as competitions. Aim to get ahead of them in the first four strides and then hold them off.
As for stronger shots... concentrate on hitting 'through' the ball ensuring the ball comes off the top of your foot - for power.(not the side or the toe) Don't stab at it. (Hit through it and follow through with your leg) To keep it down, keep your knee forward of the ball as you hit it and plant you non-striking foot level with the ball. (to stop it 'lobbing') Again, line up a row of balls across the penalty area and just hit them as hard as you can. The more you do this the more fluid your 'strike' should get as your timing improves. (practice with both feet!) The top players develop power - and perfect their timing - simply by hitting as many shots as they can. for a bit of extra fun... find a goal keeper who wants a bit of shot practice. If you are a striker, do this for at least fifteen minutes (or more) at every practice. Even if it means staying on later or arriving earlier than everyone else.