CC1101: Could you audit my pcb?

Hey, I'm new in RF design and would like to make a pcb with CC1101. I use esp32 micro controller and cp2102 in UART communication. All passive components are in 0402 packages, RF chip is connected via lines with 0.254 mm width, and 6 mil gaps between lines. In my production I'm gonna use FR-4 with 1.6mm thickness. I'm interested is it ok to have bypass capacitors on the bottom side and connected through vias? Also I looked at other boards and all of them use vias on the polygon, connected to the GND. What for they do this? and I placed vias too, is it ok? My aim to get 433 MHz transmitter/receiver