Welcome to Pherotalk. 
You have indeed found somewhere to get your edge - and it is just that, pheros won’t do all the work but in conjunction with the right behaviours, they are very helpful!
So its not too good to be true - You will find there is a fairly straightforward learning curve to find your effective doses and get the best out of pheros, to that end, you should have a good read of this thread:
Which covers all the basics of choosing and using pheros effectively.
Now to the rest of your questions:
At your age, Ammo is probably the better phero to start off with as it is a balanced mix of all the three main pheros that gives a sociable/sexy/confident/masculine impression that is suitable for most social situations. TUTH however has the same amount of none but no balancing pheros and is mainly intended for people in an established sexual relationship. TUTH can be useful in clubbing/uninhibited situations but for day to day wear it is often too much as its none content can repel as effectively as it attracts - Girls around your age tend to be responsive to less/less overt none signals and this is where finding the right dose and mix is very important.
So to the socials - and it is no problem to wear several together, just give the sprays a couple of minutes to dry between each layer. Don’t spray alcohol-base over oil though, keep those points apart.
Instant shine is a social/happy/confident and feelgood mix that goes very well with Ammo and many other pheros.
IO - Promotes flowing convesration.
IH - helps deepen conversation and increases personal bonding.
IG - is a light smooth/suave/status mix that is probably more suitable for your age than A314 - Which gives a much heavier/older/more serious/daunting vibe. Great for work but can put younger women off you in dating as it is very much a keeper/LTR signal.
Yes, pheros can stink - In use, some can break down to rather unpleasant smelling byproducts after around eight hours or so and some people are just very sensitive to the smell. You can get used to freshening-up for the former but there is not a lot wecan do for the latter. Most people don’t get it so bad though.