If you click on the link I posted in my first message, you can see all the drugs that are currently licensed for RRMS. They are split into ‘moderately’, ‘more’ and ‘highly’ effective.
It sounds like your neuro and MS nurse have decided you should move from a moderately effective drug to a more effective one. And within that group there are only the three you’ve mentioned.
Many people do manage to take Tecfidera quite successfully. And without big changes to lifestyle or bad side effects. But I can completely understand not wanting to take something that initially at least can have some iffy side effects (stomach issues), and potentially more serious ones (low lymphocytes etc).
You could ask your nurse and/or neuro whether you could take one of the drugs from the ‘highly effective’ group, ie, Lemtrada, Tysabri or Ocrevus. It’s possible that you’d fit the criteria. But the potential for nasty side effects increases with the greater benefits offered. In particular, Lemtrada does have some pretty crappy long term side effects (like thyroid disease), but an excellent relapse reduction rate.
It really is a question of 1) what will your neurologist prescribe for you, and 2) what side effects are you prepared to risk.
So, in your situation, you need to see what options are open to you and research the drugs as well as you can. Start with the MS Trust Decision Aid tool, but you could also look at the forum on https://shift.ms/ as there are lots of people on that site who’ve taken the various DMD options and posted about their experience.
Best of luck with the decision. Don’t forget, whatever you opt for, in general if you find it doesn’t suit you, change to another drug is possible.