I don’t use DTTG much, so don’t have anything useful to contribute for your particular combination, but I do use the Boox Max Lumi with DT on desktop as my main combination of document management and reading tools – indexed document collections on desktop for search-based reading, and moving single documents manually to the Boox for sustained reading. Since you’re normally only doing the latter with one document at a time, I haven’t found it inconvenient simply to transfer documents manually with AFT, singly or in batch selections, but I’m not sure there’s an easy way to do that from iPad; I suppose I’d be looking at a cloud-based workflow, maybe using the Boox’s custom version of Evernote, but it would need thinking through.
I also sometimes use the Max Lumi’s Monitor function to host a DT window on it as an e-ink second monitor, though the resolution settings on the Lumi are rather frustrating (especially in portrait orientation) even with SwitchResX. But it’s a wonderful device, despite the sometimes rather clunky onboard software (especially for document annotation, which is very awkward, though the handwriting recognition is surprisingly good). Once you’ve experienced double-page PDF views on a large-screen e-ink reader, you’ll never go back. I don’t use much third-party software on it, but @tja will be amused to hear that Wotja runs brilliantly.
Boox have now got into the e-ink monitor business in a serious way with their Mira series. I’m keenly waiting for the Mira Pro to become available outside China; it looks like it’s what DT was made for.