Water dispensers: does loading style change tank space?

It's what the tank holds at one time. Avalon's volumes don't say how quickly a dispenser heats or chills fresh water after you draw it down, so a bigger tank means more stored water, not a promise of continuous hot or cold output. The four top-loaders are the A1, A10, A11 and A1 CT. So a top-loader suits you if 3 L of chilled water is enough, and a bigger reserve means going bottom-loading or bottleless.

Avalon's A3F page title calls it bottleless, but its description talks about bottom loading with a 3-gallon bottle. With the two in conflict, the supply type is left blank, so it can't count as a match when you pick one; its cold and hot tank sizes still show. Ask Avalon which setup you'd receive before you order.

Neither. Filter performance and installation needs aren't covered for any of the ten, so for a bottleless model read its setup requirements and refill method on Avalon's page, and match any replacement filter to the exact model in Avalon's documentation.