As apparently there are many HWs but nothing is good/ still something missing something else etc... I was thinking to run ESXi on my server - so isn't it better to just virtualize openwrt (as a router) as buying another hw ...
Server running ESXi will run virtualized TrueNAS and bunch of other VMs.
I'm running OpenWrt on an ESXi -Host for some years now without problems.
If you have a reliable server, you could go that way. Just take care that the NIC(s) won't become the bottleneck. With a 10G-NIC you could use VLANs to seperate WAN/LAN-traffic.
At least for non-enterprise environments, there is something to be said for running OpenWrt on bare iron hardware with 2+ network cards, namely ease of use. Just a single device and software stack to take care of, easy to replace in case of problems (even older devices that won't reach full speed can fill that gap over a weekend), easy to get internet access for the more complex stuff to build upon (or bootstrap).
Virtualization is great, but I wouldn't want to run my internet gateway on that - as you basically have to duplicate your networking/ VLAN setup on the host server and the OpenWrt VM (both using quite different semantics) and because of the bootstrap problem (many things want internet access, but first your router VM has to boot - everything, including the host server wants an IP address, but the DHCPd only comes up after host and VM are fully booted up, etc.). If you're in an enterprise setting, you can throw hardware (including hot-spares) at it and clock in the maintenance overhead - at home, it just complicates matters (and often reduces performance). While this isn't an issue for testing or providing a vrouter to your VM stack, basic internet access imho needs more inherent reliability and dependability.