The only tip I’d pass on to the OP at this time is to ensure that, from the beginning, you have your individual journal entries usefully named in DEVONthink. For example, for me at least, it’s essential to be able to order them easily by date. If you want to do that take a look at part of this old post of mine (the first paragraph under "important warnings”).
If you get that sort of thing right, at the start, it saves much pain later.
In passing, other joys of journals in DEVONthink are DEVONthink item links to other journal entries (i.e., cross references in your journal entries) and the ease of adding photos (if, of course, you wish to do so).
Journals in DEVONthink, if not actually journalling in DEVONthink, are a wonderful resource. I wish you much luck and enjoyment.
Stephen