Optimizers? I'm pretty sure that the basic Tigo is just a module add-on switch that opens when it doesn't see the dead man signal on the DC conductors. SMA is going to build the signal transmitters into the inverters, so that's all you need for now. Pretty soon many (most? all?) module manufacturers will put the switches in the junction boxes so then it will be back to business as usual.
Tigo has a series of module-level power electronics (MLPE) devices, based on how complex you want their functionality to be.
F for Fire Safety is the basic rapid shutdown part, relying on a power-line carrier signal to communicate the "stay-on" ("heartbeat") signal.
S for Safety is also a rapid shutdown part, but uses radio signals to communicate instead of power line carrier. It also has module-level monitoring.
O is for Optimization, which is like the S-units, but will also perform module-level optimization. It can be mixed with S-units in the same string, where only selective optimization may be needed (such as local shading).
L is for Long Strings, which is like the O-units, but also allows strings in excess length of the standard sizing calculation. It is only available built-in to the module, rather than as an add-on for the installer to mount/connect.