You need to know your SAC (Surface Air Consumption) for the diving you’ll be doing, how deep and how long to pick a size.
If you’re cave diving with a scooter your SAC will be lower but the rule of 1/3’s figures your scooter died and you are swimming out.
If you are going to be entering wrecks you sure don’t want twin 150’s. On wrecks it’s common to sling tanks and leave what you’ll need for the accent and deco outside, just remember where!
This is why I use a BP&W, I can config a 72 for a beach dive or twin independant 80’s and sling bottles for something deeper.