Yes, the Brompton feel more reactive than other folding bikes, even folding bikes with (almost) the same wheel size like the Birdy.

But its just a matter of get accustomed to that feeling.

I am curious about the "11 speed derailleur (Hong Kong spec)" configuration.

Can you explain what it is ?

You mention a 9-42 cassette, this means that it should have a rear hub with something else than the usual Shimano/SRAM freewheel, is it a XDR freewheel like on the lightweight option ?

What derailleur is used to accept a 9-42 cassette the Dura Ace of the lightweight won't fit (it theoretically already doesn't accept the 9-34 cassette of the lightweight).

Last question for backers having access to the forum: are there any news about the announced front carrier block for Helix ?

For daily use of he bike and even for traveling, a front carrier block+front bag like on the Brompton (and now on the Birdy) is really a must have.

For the suitcase and remaining below the 62" linear inch limit, a solution could be to swap the wheels for ETRTO406 what would also solve the tire problem (besides the Riteway only available in Japan, I do not see any road tire in the list, only cyclocross and BMX tires).
The difficulty to change the wheels is the proprietary front hub.