Mate, pretty much all boot camps will follow the same pattern which will involve getting all candidates up to an acceptable level of fitness. In my experience (I’ve done 3 inc military and police) this involved daily workouts (Mon-Fri) . Yes, the training was rigorous and stretched most people ( there’s always at least one racing whippet 🤣) but the vast majority managed to achieve the required level.
If you did the Lympstone course, I’m sure you’ll already be at a higher level of fitness than most basic recruits to the RN. I wouldn’t worry about the phys sessions during your new Phase 1 course, they’re unlikely to be as tough as the Commando ones! But good luck with the new chapter, it’s no disgrace to attempt the RM course and fail to achieve the highest standard.