Currently I am using RB260GS as my VLAN switch and ASUS RT-AC68U Merlin as my router.

Now I want to replace the RB260GS to a router with VLAN switch feature, it seems that hEX S should be a good choice.

Current Config Future Config Questions

In hEX S Block Diagram (Switch Enable), I see there are two route to Switch Chip.

I am a bit confused on the Not Switched Ports Route, assume I am not using SFP for WAN (use hEX S as VLAN Switch), it seems that I can only get 1Gb/s as all port should be in the same bridge.
No route will be gone through the Not Switched Ports Route?

Besides, can I use hEX S as VLAN Switch + Router (Future Config)?

I also see that hEX S does not have Bridge DHCP Snooping, will this be a problem?

I really dont think a hex will be a better switching option in this scenario. If the RB260GS an actual managed switch is working fine, dont bother.

As I need to change my Wi-Fi Router to AP, I must have a router. Do you have other choices which can do VLAN switching and simple routing using one device?

IMHO decision is easy.
Do replace 260GS with hEX. If it would fit your needs as replacement then stay with it. If not, just go back to 260GS as a switch and use hEX just for routing and DHCP in place of ASUS.

Okay your explanation was confusing.
I though the hex would be acting solely as a switch to replace the 260GS.

Now its clearer you are removing the ASUS router and just using it for its wifi and using the hex as a router.
You want to know if you can also replace the RB260GS as well at the same time.

Yes, the only issue may be port limited but if not a problem,,,,,,,,,,,,,,,,,,,,,,,

The hEX S is great device actually, we used a few of them in past. But it's just hard to recommend MIPSBE – clearly MT's focus is on the ARM platform.

Wouldn't a hAPax2 be better here as it be more "future proof"?

(Even if you don't need the Wi-Fi, it not bad to have a backup and/or "management" wifi either. hAPax2 give you ARM and like similar/better performance as hEX S)

I need VLAN switching, the switch chip of hAP ax2/3 is IPQ-PPE which does not have VLAN Table, so hAP ax2/3 are not the choice.

The hEX R is fine router, just getting dated. As I said my only hesitation on recommend the hEX is that newer RouterOS features seem to be ARM only.

And throughput is higher on the hAPax2/3 than hEX for VLAN switching, according to specs. If your plan is to use the hEX to replace your ASUS, it's going to be router too, where a higher powered CPU might be handy...

But not sure there be a difference between your existing GS260 and hEX (or hAP) if you need really just need pure L2 switching without routing.

One thing to keep in mind is that routers route and switches switch. In most cases you can use one mikrotik to do it all but it does not scale well.

Why not get the HEX S and a CRS326 for your switching needs

I don't have enough space to place CRS326...

My dream switch is a 8 Port 1GbE + 4 Port 10G SFP+ Switch in CRS112 size.