Secure , but SLOW in many cases (at the moment), read the given thread.
The OP also stated that he is going (soon) to upgrade from 350 to 650 and 650 is beyond the (theoretical) capabilities of the Hex S, the usual metric is the 512 bytes packet with 25 firewall filter rules that is 498.1 Mbps.
I know that with some configuration (fasttrack, etc.) this can often be largely increased, but having a device (like the AC2 or the AX2 that have respectively 986.3 and 912.9) that on paper already exceeds the connection speed is clearly better.
The hap ax2 is clearly the best value for money. Without a doubt.
Where are the troubleshooting topics for the hap ax2? Nowhere. Where are the topics about the hex s refresh and the hap ax s? New ones appear every day. Or at least the existing topics are frequently on top.
I think I'm gonna choose hAP AX2 but I don't like that It doesn't have an usb port so right now I'm thinking to just ditch the usb port or to just wait and get maybe the hAP AX3.
do you have a use for the USB port? It comes handy when running rather large containers. But I would not use it as "cheap NAS". Please don't try or do that. Unless you only want to use it for temporary data.
My reason for suggesting the ax2 is mostly because of its maturity, i.e. for a first device I think something not having gotchas and peculiarities, and a list of things that "will hopefully be fixed", and having to say things like "it's fine as long as you..." is valuable.
If you've got your heart set on the USB port, then the ax3 is the same platform +USB, +2.5GbE, +external antennas and clocked higher (with a significantly expanded cooling solution.)
I really don't think that USB is as useful as it seems: it can basically be used for 3G/LTE modems, or storage. Storage suffers from the normal instability of all things USB, so it isn't really reliable in practice. The other big problem is that 2.4GHz Wifi and USB 3's parasitic emissions overlap in frequency, so it's a significant task to create a setup where both USB and wifi work.
I personally think that the ax2 form factor is a really big selling point. It's small and unobtrusive, but it's very capable. Depending on the configuration it's basically good up to 1 Gbps, mostly even without fasttrack. I have mostly used them without fasttrack and with CAKE queueing, and in that setup they reach around 850 Mbps, which is probably fine for normal use.
, but SLOW in many cases (at the moment), read the given thread.