This is my take on it.... there will be others.
Velocity only matters a lot if the twist is wrong. Stabilization becomes a problem with sleeker bullets, longer means sleaker and that means faster twists required OR running the bullet faster, which can tear the jacket apart. Shot some 64 bergers in a 7 twist once, pushed too fast and too fast of a twist, not a one ever hit paper. So there are both sides.
If I was going to run a specific bullet I always twist up for that bullet per the formulas for twist. Then I can feel safe working in the parameters of the cartridges speed without pushing safety.
How do I work up a load. I shoot the bullet I want to shoot, at the distance I want to use it at. I haven't shot more than deer rifles to test zero's at 100 yards in years. My testing all starts at 200 or 300 yards and extends out.
The first thing I do is run an audette test preferably at 300 yards. Take the fastest clump and load them up in groups of 3 or 5, shoot them at 300 to reverify, then take it straight to 600. 600 can show errors better, IE I play with neck tension, seating depth and primers at full distance. Thats IF what I take to 600 doesn't make me happy.
You also may have issues with case weights, non concentric issues and so on, that generally don't show at 100.
In fact the only reason I found that some loads didn't work at all at 300 but did at 600 was a fluke, I shoot different loads, 300 I shoot a cheaper load/bullet. But one day I was shooting a 300 yard match and it was really quick switching winds, I thoughth, heck I'll run my 600 ammo and have an advantage... not at all really, it barely would hold the 10 ring....Went out and shot it scoped at home, same thing showed.. I've also got a kick butt 300 prone load, that doesn't fair well at 600, but at 300 I've shot 5 shot groups of an inch...
Good luck, Jeff
