EX3301-T0 Problems

Hi all

Ok so router has settled in a wee bit and speeds are within spec, everything is pretty smooth, im still learning about this router and its settings and 3 things spring to mind.

1 - What is the best MTU for full fibre, not sure what mine is, pretty sure its not 1500 standard as Engineer altered a few things and told me the router struggles on 1500.

2 - Ive connected a 128gb USB stick to the usb port on the router, ive tried enabling file sharing in router settings and media server with absolutely no joy, it just doesnt show on any of my devices after enabling these options, ive read the manual thats no help, that simply states nothing useful except plug in a usb stick to share files lol.

Any help on these issues would be greatly appreciated, also one final thing, does anyone know if theres a video or a guide somewhere on how to setup this router for optimal performance across the board?.

I now have my Alienware Desktop connected via Ethernet as it sports a 1gb Lan port, my Phone is wifi 6 so thats fast too, just need to look at updating my other devices for wifi 6.