Is it better to apply “undecided” to have a better chance of admission and then transfer once enrolled?
Depends upon the school and major. Some schools admit directly into the major and it can difficult to impossible to switch majors later. Some schools admit into the University first, you take some pre-req courses, need to achieve a specific GPA and then you can change majors. Some will allow to take pre-req/foundation courses and you do not have to declare a major until end of Sophomore year.
Which schools are you targeting? Look up the change of major criteria for each school of interest.
If you know what you want to study than apply for that major. Being in that major will help keep you on track and get you the pre-reqs you need to proceed.