I am building a PC in the Lian Li TU100. would it be worth going with a Flex ATX or Nano PSU instead to help with internal airflow over an sFX PSU?

I am building a small form factor PC in the Lian Li TU100 case. It has native support for an SFX PSU, but since the case is so tiny it seems that having an SFX PSU in there takes up a huge chunk of space. I have seen a few builds in this case where people used Flex ATX PSU's rather than the SFX to allow for more airflow for the internal components and then mounting fans on the back bracket where the PSU is supposed to go. I also have seen the HDPLEX-400w Nano PSU+Dell 330W external power brick brought up on some forums as an alternative to normal power supplies in smaller cases

I am torn on the fact that I want to add two fans to the back of the case as exhaust fans and allow the CPU and other internal components to have more breathing room, but I don't want to deal with bringing the power brick everywhere (This would be a portable desktop) and having the nice 7 year warranty on the Corsair SF450 along with the cheaper cost ($150 vs $90).

I am looking for other people's opinions, so please let me know what you think!

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