I'm trying to make sense of RE. First off why am I only able RE things that are in my class? Pieces that use strength for example are uncraftable by me or unavailable for research.

Second area of confusion: when I RE certain pieces it seems I have a chance to learn many different schematics from it. So I find it easier to try and learn as much from the lower matts but what I don't understand is will this only result in one level higher or do I have a chance to learn purple from green? Can I just RE green stuff in hopes of getting all the purples in that class? Is there only one purple schematic available at each level? Why cant I learn several different types of heavy armor greeves at say level 20?

To answer your first problem, armormechs can only make aim/cunning gear, orange shells for medium and heavy armor (which can be used by str classes as well) and augments with aim, cunning, shield, or absorbtion.

When you RE an item you make, it has the chance of giving you a schematic with that name and level that will have a prefix name attached to it, Critical, Overkill or Redoubt, which add stats to your critical rating, power rating or defense rating. These items will be a color "higher" in rank, so if you started with a green an "overkill underwear of roominess" will have a blue name. If you started with a blue "Digi-quartz wristwatch" it would be reverse engineered into something like "Redoubt Digi-quartz wristwatch" that would have a purple name.

Then you can RE these a step further. Your "Overkill Underwear of Roominess" can be RE'd to another tier which will give you a purple schematic. So if you learned an accuracy tag it would become "Hawkeye Underwear of Roominess" and have a purple name. The last tier of stats tacked on will be accuracy, surge, presence, shield rating or alacrity (except Redoubt, which does not get alacrity.)

If your "Redoubt Digi-quartz wristwatch" is RE'd it will remain a purple name, but will also get one of the third stats if you learn a new schematic. If it gained shield rating, it would be renamed "Veracity Digi-quartz Wristwatch."

With each RE stage the rating on the item changes, but the primary stats (aim, endurance) do not change, though occasionally the secondary stat will change when it's RE'd to a third stage, albeit slightly.

I left something out- to get the Overkill, Critical and Redoubt schematics you'll have to make and RE the original schematics. Eventually you'll get whichever one you're looking for. To get a purple schematic you have to make and RE the Overkill, Critical, or Redoubt ones. You won't learn purples from base schematics, only these (provided you started with green named schems.)

I'm trying to make sense of RE. First off why am I only able RE things that are in my class? Pieces that use strength for example are uncraftable by me or unavailable for research.

 

Second area of confusion: when I RE certain pieces it seems I have a chance to learn many different schematics from it. So I find it easier to try and learn as much from the lower matts but what I don't understand is will this only result in one level higher or do I have a chance to learn purple from green? Can I just RE green stuff in hopes of getting all the purples in that class? Is there only one purple schematic available at each level? Why cant I learn several different types of heavy armor greeves at say level 20?

It is all explained in this thread:

[Guide] Reverse Engineering