1. I only use it for read only on my phone.
2. Though size can impact load/start up performance, I have found poorly written TW macros and such to cause the biggest performance issues. Large volume of tiddlers can make the problem worse.
I have configured a genealogical solution in TW. So, TW can be used for complex data structures, but you need to be careful on how features are implemented.
1) How do you use it on your mobile device? ( For Reads and Writes)
2) How is the performance on really large files -say 10k tiddlers?