If your Axis is already very accurate, replacing a couple parts isn’t likely to improve it. 2” of barrel is not a big difference. Yes, the “normal” is about 20fps/inch. However, that doesn’t mean you are going to an additional 40fps more just because you increase barrel length 2”. If you are looking for velocity, go 26”. The Bolt Lift kit is a good idea, as is the Bolt Handle. A few of the parts you listed are simply for aesthetics. What’s pleasing to the eye. And there’s nothing wrong with that. I certainly build my firearms the way I want them to look!