I’ve done something similar when entering guitar samples but with a normal recorder plugged to the line in of the tracker.
I set the recorder to record by level trigger, then I play the pattern/song in the tracker and noodle around. After that I can stop the playback and go back to the recorder and play back the parts that I want to sample and use the sample recorder. Then I can mangle the instrument in the tracker.
It’s a pity that the tracker cannot record while playing patterns. Is one of those things that limit a lot this kind of creative process and forces you to build a complex setup with additional hardware.
Yes and no, midi tracks are still pushed in sample mode.
How do you sync the IPad with Polyend Tracker?
There are so many cool apps for IPad for both generating loops but also core Sounds.
Example:
Koala sampler
eSPI
iELECTRIBE
PPG Wavegenerator
OXI One
Digitone, TD3, TR9, mod dwarf.
1010music really makes some interesting devices. I was thinking about their Blackbox, as a good mate for the Tracker due to, that it is compact and can handle poly Per track 
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That’s a very great little machine, I wish itself had a tracker type sequencer, so definitely they fir well together. You will still feel the need for some controller though, that you may connect to the Blackbox’ host port.
I saw the Youtube videos from Martwy Robot, the usage of a old sampler like Akai S3000XL or S-6000 sequenced by Polyend Tracker is also interested.
https://www.youtube.com/@martwyrobot/videos
Many of the old samplers are going for peanuts, when they have not been hyped
I got the Korg ARP 2600m, it really works great with the Tracker