Dear Customer,
Glad to get your message.
In Titan One 2.0 case,
you can use (L)210mm~255mm(max) PSU。
https://lian-li.com/product/pc-o11-dynamic/
In Titan One 2.0 MINI case,
you can use SFX or SFX-L PSU.
https://lian-li.com/product/o11-dynamic-mini/