I went through the same experimental process as you when i first started out as a CRA. Tried briefcases, rollers, backpacks, duffels... Parroting the praise of a backpack.

At first i went with a Samsonite briefcase but it was to bulky for my taste for moving around at times. I ended up going the route most of my male colleagues went and just use a backpack.

Carries everything I need and then some with the bonus that if I only have to be onsite 1 day I don't have the added heft of extra luggage while traveling. Less luggage to worry about the better.

2 day IMVs

https://www.aersf.com/flight-pack-3-black

1 day IMV

https://www.amazon.com/gp/product/B085Q5N7TH/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

anything more than 2 days, I opt to use a roller paired with a smaller laptop bag and just bring the essentials as per my day agenda on site.