I have the OP-1 too and it’s an experimentalists playground. I love it. I heard someone once describe it as a “portable radiophonic workshop”. But it does present the following major issue: Using it with other gear requires a USB-Midi host (Oplab, iConnectMidi). So to combine it with the Microgranny would require a bit of extra work or gear.
That said, there’s a lot of cool Musique Concrete things you can do with the OP-1’s tape, sampler, and tombola. Check out this thread I started on Operator-1 - https://www.operator-1.com/index.php?p=/discussion/1688/op-1-tape-vs-makenoise-phonogene-for-concrete-ish-things
You said it’s important to have a machine to use in live situations. The Machinedrum far outstrips the OP-1 here with the kinds of manipulations you can do on the fly with the parameter settings, with having 16 tracks to mute (including the ctrl-* tracks). MD has Midi out and through. It has multiple outputs, and two inputs that you can use to control or add effects to other gear. You can stuff kits full of MIDI machines, drums, or a mix of both. You can easily switch between patterns and do long songs.
Then again, an Octatrack is going to give you very similar things - it can act as a mixer, has all the MIDI sequencing, and has the ability to sample and manipulate on the fly…
Hm.
I still say experiment with the Machinedrum. Look at making glitchy sounds with the E12 machines. Give yourself as long as possible with it. If you want something good for live shows that you can use now, keep the Machinedrum.
If you’d like something more for composing and experimenting, and can come up with a financial plan to get an Octatrack later, get the OP-1 and forget about the Microgranny (the Microgranny is great but I think it’d work best as a Machinedrum companion). The OP-1 will give you a fun synth that you can resample later when you get the Octatrack.