Foxtrotgolf once you get your frozen ATPL what you really need is training, a lot of flying and a lot more training.
Ideally you would want to build hours somehow, try various different propeller aircraft and different types of flying but then (excluding military flying) your best chances of building up knowledge, confidence and airmanship is at an airline with a good and well estabilished training department, experienced instructors, good facilities and a positive training culture. So that would be my advice to you.
When you have a few thousands hrs and possibly a command, then change to wathever job you fancy.
Good luck