I wonder

1)should I increase the endurance to 10 at level 1?

2)A dweller with E10 at level 1 then level up to 50, another one who is level 50 with E 10 (I got from lunchbox)

which one has more HP?

1) I've learned from these forums that if a Dweller has 10+ Endurance, there is a bonus that is added to their HP each time they level up, so I'd say that leveling a 10+ END Dweller from Lvl 1 to 50 is a good move.

2) Taking into account the reason stated above, I'd say the Dweller who had 10+ END from Lvl 1 to 50 will have more health than the one you got from the lunchbox (Lucky find, btw!)

Thank you for your reply.

I have 7 Endurance outfit.

Put it on and then send to wasteland, to level up.

There's a rundown of how the endurance/HP thing works https://www.reddit.com/r/foshelter/comments/3ibkjj/endurance_affects_hp_only_during_leveling_not/.