To me, the titanium versions of the Delica and Endura are absolutely the best variants, whatever blade may be sitting in their frames. They are incredibly slim and light yet incredibly sturdy feeling, and of course have no nested SS liners. They are not nearly as “grippy” compared to the FRN or G10 versions, but they’re not intended for hard use anyway - they are very gentlemanly.
As for blade swaps, you should have no problem swapping other blades with different steels in, all of those dimensions are standard across the lines (make sure you also swap the mated lockbar). Here’s my Ti Delica frame with a Lil’ Matriarch blade in it, which to me is the coolest version I’ve made of it. The frame has sported several blade steels and shapes in it (standard and Damascus, wharnie, Lil’ Mat...). I’ve also so far swapped nearly every K390 blade into nicer scale setups, it’s really an amazing steel and they’ve ground them so slicey thin with fantastic factory edges. There must be a new sheriff in Seki these days! Cheers, Radioactive