I have had a little look through the forums but feel as if I should ask about things that could help, such as what materials are best for lasting armour, how much these things usually cost, what equipment is needed, ect.
If you check out under tutorials and then tutorial index you will see a detailed list on different guides that will help you along.
If you're looking for long lasting armor, pep is the strongest but takes the longest, it is also more expensive if you do the whole suit pep because of fiberglass and Bondo costs more. Also it will take you a lot longer to do this method.
Foam is good for getting a suit done quicker but I'd a bit more fragile because it's foam but you can reinforce them a bit. This is why I made my helmet with pep but armor is foam
3d printing I have no experience in so I can't give you any info there.
I'd second pep being the strongest/most durable but it also depends on how you treat the stuff.
I can yeet a foam helmet across a room and know it'll be fine. Pepakura if treated well will outlive you. 3D prints if made from the right material can be extremely strong but it's often a stepping stone to moulding and casting objects which is generally a more durable/easily replaceable alternative.
Prices of tools are generally the deciding factor. Good quality tools for a pep build are dead cheap and you can pull off a SPARTAN-III for around $500 if you try but the time investment is huge. Foam is in the same ballpark as a pep build for setup costs but the time investment is a bit lower per suit, just expect to build one or two before getting to a point where you're happy with the end product. 3D printing a full suit can be done for about $500 but the number of pieces and huge number of assembly and sanding hours is daunting, get into the $1000-$1500 range and a suit will be considerably quicker to produce (400-500 man hours and ~2months of machine up time). Moulding and casting, take out a small loan or sell your car to build one suit, then make dozens more that are identical to recover costs.