Neither the AR or A4 send MIDI sequencer data. The A4, however, has CV/Gate outputs that allow you to sequence voltage controlled gear. So, if your Sub Phatty has CV/Gate inputs (which I believe it does), then the A4 would partner with it better than the AR if you would like to use it for sequencing.
No, the AR has no Midi seq out, only Sync out to Start another Drum machine in Time. The A4 has full Midi out and CV out.
But the only true Seq. Weapon is the Octatrack
A4 is great for drums, and you can really stretch it out when using the ‘multi map’ mode. In this mode you can assign a patch to a key on the keyboard, essentially giving you a 128 voice drum kit. But you are still limited in the number of those voices that can play at the same time depending on how you set up your polyphony (it can be from 1-4 voices at a time). So even though you have 128 available voices, only 1-4 of them can be played at once. You can really dial in some amazing drums because you have much deeper control of synthesis on the A4 over the AR, but you lose in polyphony what you gain in control.