Can I replace Zyxel T50 by, actually, /any/ router via vlan set up on a switch?

Good evening,

I recently ordered a mesh system that consists of four routers to cover all rooms in my house with (hopefully) decent WiFI 6 signal. Apparently this system can only mesh when the main unit is used as a router ( = not in a bridge mode). Otherwise it would act as a number of disconnected access points which may make an automatic switching between routers difficult (for example, when walking between the floors, or going outside to the garden, while still watching Netflix on your phone). Scrolling through this forum I’ve learnt that T-Mobile distributes their TV / VOIP / Management via different VLANs. A couple of routers were mentioned in a guide (Draytek and something else) that may replace a standard Zyxel T50. There was also a guide to set up USG for this purpose.

Both USG and Draytek were able to deal with VLAN’s internally. My ordered routers, apparently - not. There were other solutions as well, DMZ, port forwarding, etc, which I even started considering…

While still waiting for my order, I’ve decided to test something. I took a switch, set up port 1 as a trunk port for VLAN’s 100, 300, 640. Connected an ethernet cable from a mediabox to port 1. Specified port 2 as an access port. Connected my (old outdated) Apple TimeCapsule to it, connected using DHCP, got ip address 85.144.somehting.something, selected router mode “DHCP and NAT”, set DNS to 8.8.8.8 and got the Internet. The speed was also ok.

So now the question comes: since my knowledge is very limited (limited to those random YouTube videos I watched), am I missing something? Is it dangerous to connect like this? It looks like this method is suitable for, basically, /any/ router out there. And if it is indeed the case, what would be the rationale for someone (in similar situation) to bother with DMZ (although, it is just one line to set up) or port forwarding?

Kind regards,