Still on multiclassing...
I actually quickly spreadsheeted some damage numbers for a pure monk vs the Rogue1-dipping shady monk.
shady monk uses a scimitar/shortsword combo (to get Vex+Nick+sneakattack)
pure monk just uses a quarterstaff (to get d8 damage die)
(ignored crits and Ki use and that sometimes sneak attack conditions aren't fulfilled, because rough sketch)
lvl | shady monk | pure monk |
2 | 13.35 | 9.1 |
3 | 13.35 | 9.1 |
4 | 13.35 | 11.2 |
5 | 15.75 | 15.05 |
6 | 23.9 | 17.85 |
That's a big jump at lv6, and the shady one is not just consistently maintaining a higher damage output, but also having double-Expertise to show off with. But... that shady monk isn't
ridiculously stronger, if you value earlier access to new features over Expertise (like your second subclass feature at lv6 being something great), and (heavily campaign-dependent but could be crippling) not having to worry about finding two specific types of magical weapons (as Empowered Strikes doesn't apply to monk weapons).