Minecraft Forums

'Best' or 'most efficient' can be measured in various ways: blocks per hour; blocks per unit area of the farm; blocks per unit volume etc.

Assuming you aren't trying for maximum possible efficiency (by whatever measure) and just want somethingthat will keep you well supplied, something roughly like the set-up you have will work. [If you're playing in 1.13+, a zero tick farm eg https://www.youtube.com/watch?v=NkV9iXii9_4 will be unbeatable, but is moderately resource intensive and may not go over well with the some servers (can be laggy and may be considered cheaty) ]

If your main concern is "almost 100% lossless", leaving at least a half block of space above where the cactus will grow and increasing the spacing will reduce losses caused by the cactus item falling on or against a cactus block.

Using thinner blocks to break the newly formed cactus also helps (glass panes, iron bars, and end rods being among the best), as does using only one 'breaker' for two cactus.

Unless each layer has its own collection system (effectively making each layer a separate farm), farms that stack cactus will also increase losses.

You may find output per hour loaded a more important consideration: 200/hr with 50% losses yields 100/hr (and is probably easier and cheaper to build) than 110/hr with 9% losses…

(I generally hang a layer of cactus over the top water floor of iron farms (or the collection chamber for cane farms, etc); this isn't particularly impressive in terms of drops per hour loaded, but it's cheap and I don't have a use for large amounts.)

This Most Efficient Cactus Farm Designs from ilmango is a nice review of the parameters involved for a number of builds.