I have a B12 deficiency, and know 2 others who have one. I'm glad I never took too much folic acid, since long term B12 deficiency can be terrible. Well, so can the short to mid term, but it's less likely to be permanent.
Those who have B12 deficiencies do need to be careful. I have only read about this, not lived it. But my understanding is that if it goes undetected, it can cause paralysis.
Glad to hear you are taking care of yourself and being informed.