My RB3011 wan is connected to ISP vdsl router via a pair of SXT5ac (claiming 650Mbps-80MHz/2S/SGI radio channel), more than enough for actual 20 Mbps internet speed
I'm planning to switch to a 1Gbps optical fiber ISP connectivity, what's the rigth hardware choice for a new radio link (120mt) supporting the new speed ??

Something from 60GHz product family.

Or dig a trench and install SM fiber, so you can extend the fiber link to the place where you'd like to use it.

Thanks
Installing and splicing optical fiber is a part of my job, unfortunately radio link is because of public property road to be crossed....
I'll go for 60GHz radios.

Well, fiber is arrived.
Locally tested @ 950 Mbps.
Over SXT5ac radio link I can't get over 230Mbps , is it an expected speed for the described radio link ?

it is, give or take 20-30mbit. at 650mbit sync, you don't have enough "clean" signal to get more, and even it was 866/866 it would still go max 300mbit.
get yourself a wireless wire set, or a set of cubes if they enter your budget. but for 120m a wireless wire set will work well, if you have los of course.