Imo it is the best smg both in slot and overall, best kinetic alternative is probably Unending Tempest. There are no objectively right or wrong perks but in general I'd suggest Keep Away, Zen Moment, or maybe Dynamic Sway for the left column (some people will try to tell you Killing Wind is good too but imo it's not worth as it doesn't last very long and Shayura can already get pretty much max range), and either Kill Clip or Target Lock for the right column depending on if you want kill chaining or more consistent 1v1s. For stats pretty much just go max range and for mods either increased zoom or range/stability ballistics. It has 3 origin traits, in general I'd say Nadir Focus is the best as it passively gives range and accuracy as you shoot, the other have niche use cases but won't be helping you every engagement like NF does. One final thing is that you shouldn't worry about trying to get a perfect adept roll, at least right now the difference between adept and non-adept is practically placebo so a good non-adept roll will still be better than an okay adept roll while being much easier to obtain.

For middle slot, yes. Top slot is either Immortal (also Trials) or Multimach (Iron Banner).

I’d say it’s the best in slot. 600’s just feel the easiest to use in the current sandbox.