After watching all of his throws:
I think he executed the short game very successfully. Not to be taken for granted at this level but he hit the WRs and RBs at the LOS with passes with very good accuracy, leading them down the field to quickly start picking up yards.
His intermediate game was more of a mixed bag, some great throws (think the RPOs to Mitchell) but a few balls that were a bit off target.
His deep balls (and some other passes) were poorly timed and/or underthrown. Some were completed after great plays on the ball by the WRs/TEs and some weren't. Development helps him hit these balls on time or with proper depth on the throw but I am not sure we get that type of growth in 1 week.
Sark said the INT was also due to the WR running the wrong route. I do think it is at least partially on MM because that was an ill advised pass off his back foot with no juice on it.
I don't put much blame on MM for the fumble. Brooks and Conner (pulling to the right from his LG spot) were supposed to double the edge and Brooks allowed him to get to the outside. MM perhaps could feel that pressure but hard to do on that play as he is turning around to throw the screen to X. Bad execution and perhaps too complex of a play call in that situation.
Overall he made good decisions and mostly threw good balls. About what you'd expect at this stage for him. If he can improve marginally over the next few weeks the offense should be able to find a decent amount of success.