The OP's proposed setup will exceed rec's by one tooth.

I've worked on 10sp bikes where a 13-29t exceeded the short-cage Record derailer's rec's by fully 3 teeth, with but a trace of pulley contact, so would expect a med-cage to handle 12-30t without complaint.

I don't see much variance in dropout hanger length on contemporary frames, almost none, but the use of horizontal dropouts will allow adjustment for better or for worse. I don't expect such good shifting with the axle slid back in horizontal dropouts.

And hopefully the OP won't be using the near-entire range of the cassette while in the small ring, that's just wrong imo (crossing from small-to-small), but many of today's gearing setups encourage this if the rider isn't fast enough to fully use the big ring. At least this can be the issue that the big 12-30t cassette (and a compact crank) somewhat solves imo.

I can recommend the OP's proposed fitment, even with a compact, if the rider isn't wanting to run too far into the small-small range and respects the limits of minimum required chain length (+2 links) when setting it up.
The other methods of chain-length sizing are not safe when using sprocket sizes outside of the rear derailer's prescribed complete gruppo.