The answer to the first question.
Everything depends on the capabilities of the ISP.
Can you connect directly to an SFP on the modem of your ISP?
On Mikrotik you can connect with PPPoE or a DHCP client ore with a static IP-adres.
The second question, you can turn off the LCD function.
Good question. I have not been able to and that is with two different providers fiber 1gig up/down or plain cable 100 down 30 up.
I didnt try with the sfp port just the spf+ port. The sfp ports work fine on the rest of the LAN to other SFP devices with both unifi and MT rj45 cages.
Note I was using the MT spf+ port rj45 cage (not fiber connections), as both lines coming from modems are ethernet.
I put in a ticket with MT in Septemberish time frame and provided data and have heard nothing.
In other words, I would buy only if you have a return the product path at no charge - assuming this is a critical function for your, for me its more of playing around.