With a Savage, I only consider the alignment from the lugs forward. Everything behind will not affect the result as the bolt head is 'separated' from the rest of the action. yes, the movement in the bolt body when the sear drops has no affect on the lock up of the action.
Most Savage actions are very straight from the factory so what little is offline, can be taken up by the bolt head.
The floating bolt head must make full contact with the receiver. Pretty common to see lugs that seat with 90% or higher contact after some use. Never done any lapping. the design does the work for you.
I have swapped bolt heads between multiple actions with zero lock up issues.
I have yet to shoot a Savage and I have shot quite a number, where the bolt face was not square enough to the lugs to cause the case head to be bent. Unfortunately, I can't say that with some Rems I have used in the past.
I have used some very toasty loads so this would surely have shown up and I have never had a problem from a 223 to magnum. And I have been able to use the same batch of brass in several actions.
As for the action threads, I have built F class and LR rigs using both shoulder and barrel nut headspace and have yet to see any alignment issues. Or accuracy differences.
I did a test a few years back where I swapped a barrel between 4 actions manf over several years (headspacing using the nut has advantages) Used the same ammo and got the same results. Even swapped complete bolts. Not bad, not bad at all.
None of my actions have had any work done to them except for bolt timing. Shooting groups in the 2's (with the occasional 1's and even a rare zero) at 200yds, inside the V bull, and under 1/2 min at 1000m is good enough for me.
I am presently competing with a barrel nut headspaced Shilen prefit and they are shooting as well as my shouldered headspace rigs.
So to the OP, bedding would be the first and most important improvment you can make to your factory rig. The factory stocks need help - ALL of them.
From there, a quality match barrel prefit will allow you to shoot very nice groups close and far.
I use the factory recoil lug and have yet to see any problems. I have also worked on a number of CGN members rifles and have yet to have an issue bedding these lugs. so far, not a single complaint on shooting performance.
maybe, the Savage recoil lugs are flat enough from the factory? I have never bothered to measure as I have not run into any issues.
I have had the pleasure of shooting Savage actions built as far back as the 80's and they all share similar traits.
Perfect, of course not. Most bolts can do with a bit of TLC as they can be quite clunky to operate (work is called bolt timing). There have been a batch of really crappy extractors but Savage quickly replaces them if you phone them. Preaccutriggers can best be described as heavy and in dire need of an improvement like the Timney. For match shooting and light pull, there is only 1 option and this trigger group is fussy to set up. No, you will not be getting anywhere near as light as a Jewell but for F class, it is light enough for me (a few ounces).
You have to keep an eye on the changes in bolt spacing, mag parts, barrel nuts and barrel threads from the changes done on the rifles offered over the last 5 yrs. however, the action footprint, both LA and SA, has not changed in decades.
For the money and ease of tuning for the performance you are rewarded with, I am hard pressed to think of any other action to use.
Jerry