Strengths
His passive give him huge advantage at early game when pokes at a safe distance and the burst restricts all movements.
Weaknesses
Minsi is still very weak and rarely works as a semi tank. So if opp has a hero that can burst down minsi before even ulting will get him in trouble. And his biggest weakness is his lack of mobility so he is highly dependent on positioning.
Atk spd
Rapid boots helps fast rotation and build mainly is to shred enemies.
Emblem
The assasin emblems give penetration which helps in early game and weakness finder helps to catch enemies
Battle Spell
Flicker when combined with minsi burst catches enemies off guard and steps up a perfect trap and it can also be paired up with first skill to get extra long hook. Petrify or inspire can also work but very situational but effective if done right. But flicker most flexible.
Early to Mid
The main trick to rely on passive and in early game create pressure by liking enemy. Once passive hits full stack enemy is stunned and you also get hp. Minsi is mostly good for dueling in early. Only certain heros could give him a hard time. And use hook after enemy uses thier mobilty skills to get more accuracy.
Best With Atlas
80% co-op win rate
Atlas ult can do a perfect set up for minsi ult and it also slows them down making them a sure kill.
Watch Out For X.Borg
60% counter win rate
Xborg when loses shield can slip out of minsi ult and passive cc which makes him troublesome to deal with.