Rax120 with eax15 and eax80 as extenders? How do u set this up properly?

Star topology vs daisy-chain topology is easily compared against each other, think of a rather wide house.

daisy-chain (to be avoided, if possible):

router on the outer left side of the house, one extender in the middle, one extender on the outer right side - for the right hand side extender to reach the internet, all data must pass through the extender in the middle. This causes performance issues, as each extender (roughly) halves the achievable throughput and (roughly) doubles the latencies, it works, but is not ideal.

star topology:

router bang in the middle of the house, one extender on each side (left/ right) of the house - both extenders (almost) always can connect directly to the centrally located router and are (ideally-) to far away from each other to see the other extender directly (and get at risk to switch to a daisy-chained topology, although the central router would be closer and should offer a stronger signal).

In practice, you might end up with mixtures of these topologies - be it because you can connect up some extenders (in AP mode) via ethernet or because the local circumstances don't allow avoiding a daisy-chain or at least the risk thereof (think router front/ middle, one extender on the left, the other back/ middle of the house, in a triangle setting; obviously this gets more complicated if it spans multiple storeys).

Especially in more complex settings, the mesh solutions (e.g. orbi- or nighthawk mesh) are smarter at coming up with sensible interconnects between mesh router and mesh satellites, both allowing easier configuration and semi-dynamic adaption to changing circumstances.