12 speed maybe? I went for Ultegra derailleurs (better shifting and substantially less weight) and 105 levers+brakes (no benefits apart from hood buttons). As for the rest, aftermarket cranks and rotors are better than what you get from a full groupset. Dura ace chain (fastest) and cassette is a go to if you prefer hot waxing.

I can say as the owner of bikes with R8100, R7100 and indeed R9200 that the front mechs on R7100 are not the same (R8100 and R9200 essentially are). R7100 is the older design, same as R9100 or R8000 and larger, heavier, slower.
As to whether you notice any of this on the road I would have my doubts - I can't - but you certainly can on the mech stand side by side.
FWIW the only improvement Ultegra brings over 105 that I really miss is the bonus buttons on the shifters.

I upgraded my 105 with Ultegra RD/FD already running Ultegra cassette and chain.

IMO it feels a lot nicer than the 105 but apparently that's a placebo. (My issue with 105 was I constantly had to re adjust FD and it's a breeze to setup through etube since no H/L limit screws had the whole upgrade done in 20mins?)

it was ~$300 AUD cheaper than local so couldn't help it.

https://www.aliexpress.com/item/1005006868319776.html

Hi, I could use your help again. The new headset and crown race arrived today. There were also two plastic parts in the package whose purpose I don't understand. Can anyone tell me what they are for and where I should install them?