As a 2 ltr owner who is not a boy racer, but is happy to pull away onto roundabouts safely, but not waiting half an hour until there is nothing in sight, and likes to be away smartly from the lights, you won't get the same economy from the 2 ltr as you get from the 1.8ltr. Probably about 12 mpg less on average would be fair, reading what other 1.8 ltr owners achieve which I find impressive.
If you get the 2 ltr and worry about not achieving what 1.8 ltrs owners are getting MPG wise, you bought the wrong engine.
Try and match 1,8 owners figures, you won't enjoy the drive, stressing about it. My advice is decide what is most important. Getting 48 to 56 mpg typically or 58 to 68 typically.
Don't get me wrong, the 2 ltr is cutting edge technology, Toyota have maximised the balance of power and economy with this new engine. But compare with other 2ltr cars, that is where you see the comparison. I get at least 20mpg more with the 2 ltr Hybrid, compared to my last 2ltr non hybrid. That's impressive.
Re HUD, the GR has it. I don't know if Toyota extended HUD to other models yet. I have the Excel 2019, no HUD.