Healing and mana potions are linked and can not be used together

I've also fished this up in Darkshore, in the Cliffspring River.

Exp every time until lvl 100 (turns yellow at 80 or so).

Based on my testing during Shadowlands (pre-patch through 9.0.2), here are the best healing potions at various level ranges:
Level 1: 考察队治疗药水 (can only be obtained in Exile's Reach -- the new starter zone in the Shadowlands prepatch)
Levels 2-9: 考察队治疗药水 or 次级治疗药水 (whichever is cheaper)
Levels 10-31: 钢铁部落活力药水
Levels 32-34: 钢铁部落活力药水 or 神效治疗药水 (they heal the same amount, so pick whichever is cheaper)
Level 35: 钢铁部落活力药水 or 神效治疗药水 or 治疗滋补剂 (they all heal the same amount, so pick whichever is cheaper)
Levels 36-39: 治疗滋补剂
Levels 40-44: 深渊治疗药水
Level 45: 星界治疗药水 for one level only!
Levels 46-55: Back to 深渊治疗药水
Levels 56-60: 灵魂治疗药水

*Note: If you start in Exile's reach, you have no access to mailboxes until you leave at level 10. You also cannot use the 凯蒂的印哨 toy; if you try to use it, you get an error that you can't use that item during tutorial.*

Why does it heal more than 治疗药水 and 强效治疗药水 while it has a lower level requirement?

小知识

屏幕截图

视频

次级治疗药水

物品等级：6

使用: 恢复80点生命值。 (5分钟冷却)
需要等级 2

最大叠加: 200

售价: 25

[Vendor Locations]

[This item can be purchased in] 北贫瘠之地（2），提瑞斯法林地（2），提瑞斯法林地，暴风城，艾尔文森林，和银松森林 .