If you are worried about it being straight just make it small. You will be able to handle PCB’s no problem if that is your intent. I worded it that way because Most people say they want to mill full sheets of plywood, some aluminum, and pcb’s. Sorry, I don’t know of any machine that can do that well. If you are just trying to do PCB’s make it small and you can easily dial it in.
As for the PLA a heated bed isn’t usually needed. I set mine to 40C and use blue painters tape wiped with high proof rubbing alcohol. It sticks so well I need to soak them in the alcohol to get the tape back off.