Its normal and expected for raspberry plants to send out runners, lateral roots, and some of these will turn into volunteer plants, several feet away from the raspberry patch. This is a sign of healthy plants that are strong and vigorous. You can dig them up and transplant, dig them up and compost them, or mow them down. I have transplanted volunteer raspberries successfully in the spring. If you were to try and kill the volunteers with Round-Up weed killer, some of the chemical will get into the roots, and damage the parent plant, so this is not recommended.

Cane berries need to produce new canes, if you cut ever "volunteer" then you will have no berries in two years time