Make sure the tube is 7075 t6 aluminum and it should be fine.
Buffers are all about the same IMHO, I like the KAK kit for its versatility/tuneability.
I have used cheap springs, JP springs, and Springco springs. If I had to choose one I would pick the JP tuned and polished. Less "sproing" noise in the stock, and the sends the bolt home more positively. Just check your spring length regularly for shrinkage. Usually around the 3000 to 5000 mark or about 10in. Friend has the Geissele Super 42 spring system. Over all I was not impressed. Completely proprietary spring and buffers and it did not perform any better than a mil-spec type setup. never tried the flat wire springs.
If your running a suppressor, some of the gas busting charging handles like the radian raptor might be a good choice.
I have never found a need for an ambidextrous charging handle personally, YMMV.
I have found charging handles that are slightly extended or swept forward like the Aero Breach, can be helpful especially depending on your sight setup. When running scopes, or backup sights it can be a touch hard to grab on the charging handles without banging up your finger. And in general they are just a bit easier to use.