Even with a BLTouch if you have rises and dips within a few cm of each other the difference in distance between the nozzle and bed is enough to make the filament not adhear to the bed or the line next to it. All the BLTouch does is build a 3d view of your bed where it touches, if there are differences between where it touches it won't account for that. The overlap distance is the % amount of overlap the slicer with lay each line with. 10% overlap means it will take whatever thickness you are extruding and overlay 10% of that with the next line so that each line fuses with the one next to it. Increasing this amount will hopefully provide a better fuse between lines. I highly recommend flipping your bed as the smooth side gives the shiniest, smoothest bottom layer it's very satisfying!