Until you get a better answer, I think you need more memory to move those databases. I have 17 databases with indexed content, total of about 20 million unique words, 16GB memory. In my M1 Mac search is almost immediate, but in my iMac Intel with 24GB of RAM, searches takes more time than yours. Check how much memory is using DT in Activity Monitor.
Related to DTTG, well, day to day I wonder how well DTTG works in those mobile devices, even in my iPhone. What I’m trying to say is DTTG is one of the most versatile tools that exists in iOS/iPadOS and takes most of its features. We are used to immediately answer, but sometimes that is physically not possible.