Hi all,
since the reviews and specs on the Acer Helios 500 Predator laptop (I have the PH517-51 model) are ambiguous, at least they were around 2 months ago:

the laptop has two (2) Thunderbolt 3 ports (specs usually claim just 1 port).

I connected a BMD Mini Recorder to one tb3 port (using an Apple tb2-to-tb3 adapter), plus a camera with 1080p25 over hdmi;
and I connected a BMD Intensity Extreme to the other tb3 port (same type of adapter), plus a camera with 720p50 over hdmi.

vMix sees both capture devices, and shows their video.
Delay is minimal, as can be expected with TB.
Camera's are in synch.

Render time of vMix (streaming and recording are off) is between 1 and 3 ms.
vMix 'taxes' cpu at 2% (overall around 6 with Chrome open).
Laptop fans do not kick in (running on mains power, power saving switched off in Windows).

One of the camera's does not supply audio in vMix (the other one does), but I have seen this in several situations, it has nothing to do with using 1 vs. 2 thunderbolt ports simultaneously.

I don't know if the ports can simultaneously run at max (40 Gb/sec) speed, but I guess they don't need to here (even though they just might), with just one camera connected to each port.
Any tips on how to measure/verify TB3 port speed, are welcome, though.

Cheers
Arie