I think you should read the Guide for applicants of the MSCA-PF very carefully if you want to increase your chances of getting the award.
In the 2023 edition at p. 7 they clearly state that:
Only one proposal per individual researcher can be submitted. In case
of several proposals involving the same individual researcher, only
the last submitted proposal will be considered eligible. However,
please note that the same supervisor and a host institution can be
involved in more than one proposal in the same call.
But the Guide also contains a lot of other absolutely vital info if you plan to apply!
If you need to ask any other questions, you can try to contact the National Contact Point (NCP) of your country. In my experience they respond very quickly, but I guess it can vary from country to country.
Finally I would suggest you to contact your potential supervisor as soon as possible. And keep in mind that most research institution need to approve your application first, and this can also take time.