Zyxel GS1900-24E

What type of bandwidth, or throughput are we talking when choosing to use openwrt firmware on the Zyxel GS1900-24E with a gigabit connection? Would it be worth it?

It's a switch, not a router (even if OpenWrt would technically allow you to use it as such, at abysmal speeds).

L2 switching will happen at wire-speed, L3-routing at under 15-20 MBit/s at most.

I figured this much, but I had to ask. I don't feel like wasting a day of dabbling to find out the cold truth on my own. Thank you for a prompt response.