Aquariums: Will my new tank be okay for a Betta?

I jest 😆 Betta boy is probably staying right where he is

This is a massive tank to me. I've only kept 20 longs in the past and did maintenance with a 5 gallon bucket. My plan is to use a submersible pump and a spare tank as a transfer point to reach the bathtub which is ~25' away

Not sure what I'm doing on filtration. I could run a 20 as a sump. Probably just going canister. I am mortified at the potential for an overflow or failure because I'm on a 3rd floor apartment. Property management said anything I want to do is fine – didn't even bat an eye when I joked about getting a 120 gallon

Still a week or more before I fill it. Building the stand maybe today. Just an impulse buy for now because the price was good

Stocking is undecided. Looking at Odessa barbs or swordtails as the stars (lyretails 😍) with a supporting cast of otocinclus, corydora

Thoughts, suggestions? Your input is appreciated