Much has been discussed on the topic of grease, oils and lubrication. There is no “best” choice here.
High temperature rails come pre-packed with heat-resistant “Krytox GPL 225 Grease” These greases are compatible with other PFPE/PTFE greases, but PFPE lubricants should not be mixed with other common types of lubricant. Note: The Krytox is expensive, it may be worth removing and storing as much of the pre-packaged grease as you can when you receive your high-temperature rails! Source
Standard Misumi rails come packed in “Kyodo Yushi Multemp PS NO.2” In the US it may be hard to source, but close alternative would be the AFB-LF from THK, any grade 2 lithium grease should be fine though. Source
Currently unknown which grease comes with LDO rails.
LDO Docs - Linear Rail Greasing Guide
Some of the most commonly recommended lubricants by Voron community members are Mobilux EP1 or EP2, Superlube 21030, or white lithium grease.
People are also reporting that you can use a light grease such as superlube 21030 or a oil, such as superlube 51010. Super Lube grease is noticeably quieter after switching from tri-flow PTFE oil to superlube grease. Superlube compatability sheet