...can I run a standard carbine setup with a regular buffer (3oz)?
Carbine buffers (3 oz) are too light, even when an AR is properly gassed. It allows the reciprocating mass hit the back of the receiver extension harder than it needs to resulting in sharper recoil. H buffers are good, H2 buffers are better.
Spring quality in a firearm is very important. One problem is the quality of the extractor spring. Most companies use the wrong spring which usually fail between 750 to 1500 rounds or so, especially with a heavy firing schedule. (Such as shooting a couple hundred or more rounds in an afternoon.) Be prepared to replace the extractor spring with a Colt or Sprinco M4 spring.
After the extractor spring, the springs I've seen give trouble most often are the hammer spring and action spring. However, most companies get those right.
Another important detail is gas port diameter and system integrity. Which gas port is correct depends on the combination of barrel length and port location. (Also, whether or not you plan to shoot suppressed, but that's another level of education in itself. Let's learn the basics before going down
that rabbit hole!) Gas integrity isn't hard to achieve. It's easy to make sure everything lines up and doesn't leak.
Next, just make sure the feed ramps of the barrel match. These days, almost all flat top uppers and barrels have M4 cuts. Just to be on the safe side, double check.
The rest- lower parts kits, trigger groups, furniture and sights is relatively straight forward and usually dictated by personal preference.
PS- You can save money by getting a set of drop-in handguards from Magpul other than going for the free float tube right away. That will get you shooting right away while agonizing over which free float tube is best for you- or even if you need a FF tube. Again, this is personal preference.