You can use alot of ecus. Depends on how far you would like to go.

8n0906018ch is BAM. You can switch of vvt, egt, and so on. This will work.

"how far": well, wideband O2, all tune outs (cat, egt, evap, sai, keep vvt?). Immo defeat.
For ralley cross car, totally stripped. 67mm compressor billet hybrid turbo. pump gas (regulations), 550cc, 3" maf.
Need to put a base tune on (with bench harness) before I ship to my brother (Germany).

I have a tune from a tuner here, made a long time ago for this purpose. But not sure if made for the 018CH, and it if has the correct parameters (see above).
Can I post the tune here and someone can check it?

4B0906018CH is the ecu that is most used on a4 and passat widenband, but any wideband 1.8t will work.
Also that turbo is huge for 550cc injectors

i looked quick, it has been modified for injectors for sure, and some deletes, i did not have this exact def so i did not put
much effort in it.

what ecu part number are you flashing it on?
and yes most likely immo delete will be needed if no cluster

there is pretty clear instructions up here for the immo delete

i could help with that, assuming you have everything set up. but if you can read and right eeprom you have no need for help