The GL-AX1800 Flint already has Gigabit Ethernet.
It may be possible to do link aggregation on the GL-AR750 Creta, but I don’t think it would be worth it:
- The router and/or switch also needs to have link aggregation, which are not so cheap, in order to connect 2 ports to the Creta using 2 Ethernet cables.
- The 2.4GHz wifi speed would probably not gain much, if at all. The 5.0Ghz wifi band speed have gain, but hard to estimate how much.
It may be easier and cheaper just to replace the Creta with a GL-AR750S Slate with Gigabit Ethernet.