New Large Setup, Q about plumbing, sump

[Jimothy]

I am setting up a 180g tank with built in overflow and ramp/platform for freshwater turtles.
(posting here because general setup seems most similar to reef tanks)
I have 3 red-eared sliders in a 45g with Fluval 405 set up now, the 180g is new and needs another week for the seals to harden. I hope to have everything set up by then, Saturday the 27th.





I have drawn up 2 options for the undertank setup and would love feedback on:

• Water flow through the system in general?
• In case of power outage, would these setups lead to flood?
• What type of plumbing, rigid or flexible?
• Water pump, submersed or external, what brand?

setup 1 or setup 2

If pics are too small, also attached,
Thanks for looking