If you are mounting a silicon tuner onto the main PCB you will need to let us know what frequencies it will cover and what PCB materials and stackup will be used.
Dropping thickness between route layer and gnd plane will reduce track widths, but you should try and do this around a core instead of pre-preg as it is easier to control the seperation.
If you are using a tuner module, you also need to watch if you have a single ended output at BB, or if the output is on IF and a differential or IQ output. Those routings need some consideration.
Lot more information needed really before can give good advice.
:F